All Hail the Iga Swiatek … Serve?

Iga Swiatek at the 2023 US Open. Credit: Hameltion

There are a million things to praise about Iga Swiatek’s tennis these days. This puts commentators in a quandary, because her matches are often so short that there isn’t time to list them all. She is world-class at nearly every aspect of the game.

If there is an exception, it is her serve. While it is not a liability, it doesn’t appear to stand out as a weapon, and Swiatek continues to make technical tweaks to improve it. She doesn’t dominate first-serve points the way that Qinwen Zheng or Elena Rybakina does; she doesn’t pile up aces like Rybakina, Karolina Pliskova, or Aryna Sabalenka. The longer a point lasts, the more time she has to take control, so who needs a standout first strike?

A look at the bigger picture, though, tells us that Iga’s serve is just fine. She was broken just five times in six matches en route to her second Indian Wells title. In the last 52 weeks, she has held 81.6% of her service games, best on tour.

To quote myself when Alex Gruskin threw that stat at me a couple of weeks ago: Wait, WHAT?!

Here’s the top ten since Miami 2023:

Player              Hold%  
Iga Swiatek         81.6%  
Aryna Sabalenka     79.4%  
Elena Rybakina      78.5%  
Caroline Garcia     76.4%  
Madison Keys        76.4%  
Petra Kvitova       75.8%  
Katie Boulter       74.3%  
Qinwen Zheng        73.2%  
Liudmila Samsonova  73.1%  
Maria Sakkari       73.0%

I can already hear everybody sputtering out their “yeah but” explanations, and we’ll get to some of them in a moment. First, though, we need to acknowledge just how elite this is. Sabalenka held at 80.8% last year, her best campaign so far. In 2015, when Serena Williams went 53-6 and won three majors, she held 80.9% of service games. Ash Barty peaked at 80.1%. Pliskova has twice cracked 79% for a full season, but never 80%. Same for Kvitova.

WTA match stats are sparse before the mid-2010s, so I don’t have numbers for Navratilova, Graf, Davenport, Venus Williams, and the rest. (Navratilova won 75% of total games in 1983, so… wow.) Suffice it to say, hold percentages that start with an eight are the province of all-time serving greats. Iga has muscled her way into that group.

The all-rounder

The simplest explanation of Swiatek’s serve stats is that she wins a lot of all kinds of points. As long as she doesn’t double fault, she’s in a rally, and she doesn’t lose many rallies.

This is true, sort of. In the last 52 weeks, Iga has won almost half of her return points, good for a break percentage of 49.5%. That leads the tour as well, granting her a spot in the hyper-exclusive Top One Club.

The average player in the WTA top 50 has a hold percentage about 33 points higher than her break percentage. Iga’s difference of 32 points, then, is not far from the norm. Despite winning so many service points, she is an entirely different sort of player than Rybakina (43 point gap) or Caroline Garcia (55 [!] point gap). Swiatek tacks an average serve onto a game that is otherwise outlandish.

On the other hand, it’s easy to underrate average. Most players who are extremely good at one thing are lucky if the rest of their game can pull enough weight to keep them on tour. The biggest servers are often indifferent (at best) on return; the best baseline players are rarely blessed with world-beating serves. Here are the current top ten returners among the top 50 (plus #52 Sara Sorribes Tormo), shown with their hold percentages and the differences between their serve and return results:

Player               Break%  Hold%   Diff  
Iga Swiatek           49.5%  81.6%  32.1%  
Lesia Tsurenko        48.1%  56.4%   8.3%  
Sara Sorribes Tormo   47.5%  58.4%  10.9%  
Clara Burel           45.4%  61.3%  15.9%  
Coco Gauff            44.7%  71.2%  26.5%  
Daria Kasatkina       44.5%  62.4%  17.9%  
Marketa Vondrousova   44.0%  68.7%  24.7%  
Jessica Pegula        43.1%  72.0%  28.9%  
Elise Mertens         41.0%  65.2%  24.2%  
Katerina Siniakova    40.2%  61.3%  21.1%  
Ons Jabeur            40.1%  67.0%  26.9%

If we approximate “serve-specific skill” as the difference between hold and break percentage, we find that the best returners are–unsurprisingly–generally weaker servers. Everyone on this list is below average in serve-specific skill. Among this group of elite returners, though, Iga is the best server. Only a few women–familiar names like Pegula and Gauff–come close.

Here is the relationship in visual form:

Iga clearly occupies a world of her own.

What works

One thing Swiatek does well is that she can hit her serve hard. At least year’s US Open, 40 different women had at least 100 first serves that landed in the box and registered on the radar gun. The top of the list are the names you’d expect: Sabalenka, Qinwen Zheng, Samsonova, Gauff, and Keys. Next up were Elise Mertens and… Iga Swiatek. Iga’s average first serve was a rounding error away from Keys’s and just 2.5 km/h slower than Gauff’s.

Speed matters, obviously. All else equal, a faster serve means more aces, more short points, and more service points won. The spin that Swiatek generates may make her first serves more difficult than the radar gun indicates, as well. When five-foot, four-inch Yulia Putintseva challenged the Iga serve at Indian Wells, she often found herself making contact at or above head level. Putintseva, I suspect, would have preferred to take on a flatter hitter like Samsonova, even if it meant handling a few more miles per hour.

Raw speed might also be underrated. When I dug into some ATP numbers to tease out the effects of speed and precision last month, I found that speed seems to matter more than accuracy. Equivalent data isn’t available for the women’s game (and the men’s data itself was exceedingly sparse), but it seems reasonable to assume that the relationship would be similar.

The relative effects of speed and precision are particularly important to Swiatek, because she hits a lot of her serves down the middle of the box. (Technically, those serves could still be “precise,” in the sense that they land close to the service line, but they won’t be as unreturnable as the equivalent deep serve close to a sideline.) Match Charting Project data tells us that the average WTAer hits 21% of their first serves down the middle. Iga comes in at 32%. Returners start the point on the back foot, even if they don’t have to move their back foot very far.

Swiatek gets away with all those down-the-middle serves, partly because she is better than her peers in general, and partly because she sacrifices less effectiveness than average by choosing a more conservative target. Here are her first-serve winning percentages by direction:

Direction   Iga W%  Tour W%  
Deuce-Wide     68%      65%  
Deuce-Body     64%      57%  
Deuce-T        74%      67%  
Ad-T           69%      64%  
Ad-Body        63%      56%  
Ad-Wide        69%      64%

(I use “down the middle” and “body” interchangeably here, because that’s how Match Charting Project logs are coded. Within tennis, the term “body serve” often refers to a narrower category of balls aimed directly at the returner. Iga hits some of those, but an awful lot of her serves–even her first serves–are neither that sort of body serve nor a delivery aimed at a corner.)

The average player gives up eight percentage points when they go down the middle. Iga sacrifices only six. It also helps to be so good in general. A winning percentage of 63% or 64% will keep you in a service game; 56% or 57% will put it much more at risk.

82%, here we come

One benefit of scoring so many points with down-the-middle serves is that it allows Swiatek to save the angles for when it matters most. It’s tough to pinpoint exactly what the key moments are for Iga, since her matches are often so lopsided. Serving at 4-all in the first set against Maria Sakkari yesterday, she built a 30-15 advantage with three first serves to the body. She served wide on the next point and down the T at 40-15. Neither one came back. She didn’t lose another game the rest of the way.

My hypothesis, based on watching her recent matches, was that this was a recurring pattern, that Iga goes to the corners more on key points and thus holds serve even more often than her serve-point success would indicate. But this is wrong, at least facing break points over the last 52 weeks. Since Miami last year, she has won 64.6% of serve points, but only 60.6% against break point. Most women save break points less often than they win other serve points, because break points tend to be generated by stronger returners. But a margin of two percentage points is typical. Iga’s four-point gap is not.

In fact, Swiatek was dreadful facing break point last year. A few years ago I built a metric to measure each player’s success rate at break point, comparing their break points saved to the number of points they’d be expected to win based on the other serve points played in those matches. By Break Points Over Expected (BPOE) in 2023, Iga was dead last among tour regulars. She faced 311 break points, and if she had served as well on those points as she did in the rest of those matches, she would have saved 184 of them. Instead, she saved 165, a difference of -19. No other top player had a negative result worse than -5.

Fortunately for the Polish star, this is the kind of clutch (or anti-clutch) performance that tends not to persist. Either it’s bad luck, or the choking turns out to be temporary. And indeed, in 2024, Swiatek has turned things around. She has saved 76 of 109 break points faced instead of the expected number of 66. She probably won’t sustain that level of break point overperformance, but even a neutral score would further improve her tour-leading hold percentage. If she could prove out my hypothesis and win more break points than expected by saving her best serves for those moments, she would head further into untouchable territory.

No one will ever mistake the Swiatek serve for the cannon of Sabalenka or Rybakina. But Iga’s overall game means she wins more points than the heavier hitters. Her serve doesn’t have to be great, it just needs to stick around tour average. She has achieved that, and–pity her poor opponents–there is room for her to improve even more.

* * *

Subscribe to the blog to receive each new post by email:

 

The Clutch Defense of Emma Navarro

Emma Navarro at the 2023 US Open. Credit: Hameltion

The dizzying rise of Emma Navarro continues. She finished 2023 at a career-high 32nd in the rankings, rose to 23rd before Indian Wells, and now, on the back of yesterday’s upset of Aryna Sabalenka, she could crack the top 20 on Monday.

Not long ago, many fans thought of Navarro as a vulture, riding a bunch of small-tournament victories to an inflated ranking. Now, with back-to-back wins over Elina Svitolina and Sabalenka on one of the sport’s biggest stages–and not on clay, her favorite surface–the doubters are quieting down. The American already ranks 19th on the Elo table, another list she’ll continue to climb when this week’s results go in the books.

Yesterday’s triumph was less straightforward than it looks at first glance. The scoreline–6-3, 3-6, 6-2–hides just how close it was. Navarro won just 83 points to Sabalenka’s 80. The second-seeded Belarussian lost the match despite winning return points at a slightly higher clip than her opponent. Sabalenka’s ratio of winners to unforced errors was 38:28, the type of attack that has won her innumerable matches, and one that looks better than Navarro’s 21:16.

The underdog appeared to be the clever, resourceful player on court, making improbable returns and outlasting her more aggressive foe on the long points. Yet the numbers don’t bear out much of that, either. 20 points lasted at least seven strokes, and each player won 10. Sabalenka won five of the longest eight. Navarro’s returning won the day, as we shall see in a moment, but it was not particularly impressive against a far-from-peak Sabalenka. In the last year, opponents have gotten 70% of Aryna’s serves back in play. Navarro managed 67%.

Despite all that, Navarro walked off court with a smile on her face. What worked?

Timing is everything

The top-level answer is that Navarro converted break points, and Sabalenka didn’t. The underdog seized four of her five chances. In each game that she generated a break point, she secured the break. Sabalenka, on the other hand, earned more opportunities but took advantage of just two. She squandered a chance to put the first set back on serve at 5-3, and she could have erased Navarro’s break advantage at 3-1 in the decider. In neither of those games did the American slip again.

Break points, like points in tiebreaks, tend to be more complicated than average. Servers are a bit more careful to put balls in the court–and thus more conservative–and returners are hyper-focused. A high-pressure point is less likely to end with an unreturned serve; long rallies are more common. Navarro–with some help from her opponent–took this to an extreme.

The American, despite putting slightly fewer serves back in play than Sabalenka’s average opponent, kept the point going on each one of her five break points. She also returned every serve at 15-30, three of four at 30-30, and both at deuce. Here’s how Sabalenka’s rate of unreturned serves looks when separated by whether she was in trouble–defined as whether Navarro had already won two points in the game:

Situation       Points  Unret  Unret%  
Not In Trouble      51     16   31.4%  
In Trouble          22      4   18.2%

Even that distinction understates things. Two of Sabalenka’s unreturned serves in the “in trouble” category came at 40-30. When the second seed was really on the ropes, Navarro got the ball back on 15 of 17 tries. Pressure points are less likely to end quickly, but not by such an enormous margin.

Whether Sabalenka became uncharacteristically shaky under pressure, Navarro morphed into a return savant, or it was pure dumb luck, those few points determined the outcome of the match. In extended rallies, as we’ve seen, the American was not the overwhelmingly superior player, but that’s not the point. Sabalenka dominates most of her opponents by winning more cheap points than they do. If she wins just half of the rest of the points–on her serve and her opponent’s–she comes out on top. Take away most of the cheap points, and her edge is gone. Navarro won 24 of 49 return points–roughly half–when she put the ball back in play. Because she was so resourceful at key moments, she held Sabalenka to just 54% of serve points at 30-all or later.

Lessons

There are so many ways this match could have ended differently. Sabalenka could’ve served a little better under pressure, or Navarro could have returned a little worse. The whole scenario was made more likely by the conditions, slow-playing Indian Wells courts and balls, combined with wind that distracted the favorite more than the underdog.

Another culprit on the Belarussian side was Aryna’s plus-one. Eleven of her unforced errors came on the first shot after her serve, many of them wild and inexcusable, one of them two points away from defeat. It is to Navarro’s credit that she got so many serves back, but a more typical Sabalenka performance would have put away more of the desperate returns.

This is all a description of what happened last night, not speculation about a trend, or any kind of prediction. Sabalenka usually hits about as many unreturnable serves in pressure situations as she does at other times. In the limited data we have so far on Navarro, there’s no evidence that she is much better returning at key moments. Clutch performance in tennis is only rarely persistent: It’s easy to identify matches or tournaments when a player was particularly good or bad when it mattered most, more or less impossible to forecast it. If we hit rewind and replayed the match from the start, Navarro might still pull the upset, but it wouldn’t develop the same way.

What the match does give us is a little more evidence that Navarro is here to stay. She drew even with the second-best player in the world, staying calm enough throughout the proceedings to deliver her best tennis when the stakes were highest. She might not win a rematch with Sabalenka, but her position in the top 20–whether or not the WTA makes it official next week–is no fluke.

* * *

Subscribe to the blog to receive each new post by email:

 

The Downward Slide of Stefanos Tsitsipas’s Backhand Return

Stefanos Tsitsipas ahead of the 2023 US Open. Credit: Hameltion

Yesterday in Indian Wells, Jiri Lehecka knocked out Stefanos Tsitsipas with a masterclass of precision power hitting. The Czech tallied 27 winners to Tsitsipas’s 8, and that’s only after a belated burst of energy from the Greek in the second set. When I wrote about Lehecka in January, I chided him for an “excess of self-restraint,” hitting too many balls down the middle to take full advantage of his baseline weapons. He avoided that trap yesterday, and Tsitsipas paid the price.

Still, Lehecka didn’t seize upon every exploitable edge. The Tsitsipas backhand, pretty as it is, is a bit cumbersome, often leaving him slow to react. The time he needs to unleash the one-hander is a key reason why Stef is one of the most surface-sensitive players on tour, preferring courts that give him an extra split-second to prepare. Indian Wells plays slow for a hard-court event, but it’s hardly the same as the Monte-Carlo dirt. Combined with Lehecka’s power, a hard court has the potential to expose the Greek’s weaker side.

Lehecka generally stuck to the routine, sending both forehands and backhands cross-court, rarely doing anything in particular to force his opponent to hit a backhand. Still, the Czech made one concession to his opponent’s tendencies: He hit more serves than usual to the backhand. Lehecka’s favorite serve is the deuce-court slider wide, and he scored a few points blasting balls that Tsitsipas’s forehand couldn’t reach. But more often, he forced Stef to hurry the backhand, or chip a return.

The results were devastating. The Czech typically hits about half of his serves to each wing. 51% of his first serves and 52% of his seconds go to the backhand. Yesterday, he went that way 61% and 58% of the time, respectively. When Lehecka hit a first serve to the backhand, Tsitsipas got it back less than 60% of the time… and he won only 12% of those points. When a second serve went to the backhand, Stef got a more respectable 71% back, but still won just 14%. It was a short match, so we’re not talking about that much action: In nine return games, Tsitsipas won just four points when he had to make a backhand return.

The word is out–not that it was ever really a secret. Two weeks ago in the Acapulco quarter-finals, Alex de Minaur hit 90% of his serves to Tsitsipas’s backhand, beating the Greek for the first time at tour-level in eleven tries. While de Minaur’s persistence was unusual, it made a useful point. Stef–not long ago the third-ranked player in the world–has fallen out of the top ten, and one of the causes is something that every opponent can attack until he patches it up.

Serve this way

Yesterday’s match notwithstanding, Tsitsipas remains an elite server. He held 88.8% of his service games last year, the best mark of his career. His return numbers, though, are sinking. In 2021, he broke one-quarter of the time; last year, that number fell to 19.3%. By that metric, he’s in the bottom third of the ATP top 50.

It’s hard to pinpoint just one element of his return game that has gone astray, because everything is trending downwards. According to Match Charting Project data, he gets 66% of serves back in play–a below-average if acceptable figure–but wins just 42% of those points, one of the lowest marks on tour. Both rates are worse than his career averages of 68% and 44%, respectively.

The decline can’t be entirely blamed on a tour-wide tactical consensus, though Stef’s opponents aren’t helping. Here is a ten-match rolling average of the percentage of first serves hit to the Tsitsipas backhand on hard courts since late 2018:

(Clay courts add another wrinkle to the question, because everyone tends to get more serves to the backhand side on dirt. Four of Tsitsipas’s five most extreme matches by this metric were on clay.)

As always, it can be tough to gain an intuition with an unfamiliar tennis metric. 60% may not sound like a lot, but most servers cluster around the tour average of 52.5%. The servers who most frequently target the backhand side are clay-courters: Albert Ramos tops the list at at 63.5%, with Fernando Verdasco right behind him. At the other extreme, around 45%, are some right-handers, often those who can use height and/or wrist action to open the court with lots of slice. Daniil Medvedev and Andy Murray are two of the best-known proponents of this approach, and Medvedev is partly responsible for some of the troughs in Tsitsipas’s trend line above.

More to the point, the tour is taking aim at Stef’s backhand as much as it does anyone’s. Only Ivo Karlovic was faced with more backhand returns on hard courts. Denis Shapovalov, another one-hander, is in the same range. Again, the message about Tsitsipas’s backhand isn’t new, but it’s no accident that servers are picking on it at the same time that his return numbers take a nosedive.

Crash

Anyone who doesn’t attack the Greek’s backhand return these days is leaving points on the table. Here is another ten-match rolling average, this one showing Tsitsipas’s rate of return points won when his opponent lands a first serve to his backhand:

If you’ll forgive me some technical jargon, that’s… not good.

As we’ve seen, Tsitsipas won just 12% of those points against Lehecka. He won only 14% against Taylor Fritz in Australia and 16% in Los Cabos against Casper Ruud. Daniil Medvedev held him to 11% last fall in Vienna. And at the Tour Finals, Jannik Sinner hit 21 first serves in that direction. Tsitsipas won none of them.

Across 125 career charted hard-court matches, Stef has won 23.1% of return points on first serves to his backhand and 24.7% to his forehand. Since the start of 2023, those numbers have fallen to 20.6% and 23.4%. Every important return stat is trending downward, and the backhand numbers are declining fastest of all.

The only question remaining for Tsitsipas’s opponents is this: How much is too much? De Minaur set a new standard by going to the backhand with 90% of his serves, both first and seconds. That’s not unheard of on clay courts (Lorenzo Musetti has come close in two previous meetings with Stef), but it’s very unusual on a hard court. Only a handful of Tsitsipas’s opponents have topped even 70% in one direction.

Against most players, such a balance is probably appropriate. Too much to one side, and you lose the element of surprise. But because so much serving is split 50/50 (or 53/47), we don’t have much data to test the hypothesis. If there’s a 30% chance the server will go one way, will a returner really have an edge in the more likely direction? Against de Minaur, Tsitsipas figured things out quickly enough and inched over toward the backhand side. But not for long: The Aussie cracked one of his few forehand-side serves for an ace, far out of Stef’s reach. Tsitsipas is a good test case for servers looking to experiment: His success rate when he gets the return back in play is near the bottom of the table, so he’s unlikely to turn a match around just because he guesses right a few times.

I have no idea whether, at this point in the Greek’s career, his backhand return is something that can be fixed. In the short term, it will be easier for opponents to expose it than it will be for him to find a solution. Tsitsipas’s return numbers, already dire, could get worse before they get better.

* * *

Subscribe to the blog to receive each new post by email:

 

Yuan Yue Will Return Your Serve Now

Yuan Yue at Wimbledon last year. Credit: si.robi

Here’s an impressive stat for you: Last week in Austin, champion Yuan Yue won more than half of the return points she played. In fact, had she picked up just one more point against Wang Yafan’s serve in the quarter-finals, she would have won at least 50% of return points in each of the five matches she played.

This isn’t earth-shaking stuff: There are about a dozen tournaments every year where the champion wins more than the 51% of return points than Yuan did in Texas. Iga Swiatek won 56% at the French; Aryna Sabalenka cleared 52% in Australia. Lauren Davis won 53% in Hobart last year. The average single-match loser on the WTA tour loses about half of their return points, so it’s not far-fetched that a titlist would rack up these numbers for five or six days running.

Still, this is Yuan Yue we’re talking about. Not only was the 25-year-old Chinese woman a longshot to win the title–it was her first on tour–she has hardly established a reputation as a steady returner. A dangerous one, perhaps: In last year’s Seoul final against Jessica Pegula, Yuan turned one out of six of the American’s deliveries into a return winner or forced error. But the overall results weren’t so impressive, as she won fewer than 40% of return points in the match. For all of those big swings, there were lots of swings and misses. Out of five matches in an otherwise encouraging week in Seoul, she won more than 46% of return points only once.

The game Yuan brought to Austin was something different. Like San Diego champ Katie Boulter, she took fewer risks than usual, trusting that she could win points a shot or two later. Facing Pegula, and in another losing effort to Emma Navarro in the Hobart semi-finals, Yuan’s average return point lasted four strokes. Against Wang Yafan on Friday, return points took six. Yuan hit just three return winners in that match; in the final against Wang Xiyu, she didn’t hit any. Presumably she’s ok with that.

The magnitude of Yuan’s achievement isn’t quite the same as Boulter’s: The Brit beat five opponents ranked in the top 40, and Yuan didn’t face anyone in the top 60. Yet the week marks a major step forward. The 25-year-old cracked the official top 50, and Elo now rates her as the second-best Chinese woman on tour. If she continues to put returns in play the way she did in Austin, she could climb even higher.

One more ball

Returns in play are good, but they come at a cost. Do you aim to stay in as many points as possible, accepting that a lot of your returns will be weak, or do you swing big, piling up errors in exchange for a handful of return winners and better odds when your returns find the court?

While the pros and cons are different for every player, no one escapes the tradeoff. Even across players, there is a persistent negative correlation between returns in play and in-play returns won. If you make more, you win fewer of them. The following plot shows those two numbers for every woman with at least five matches in the Match Charting Project dataset from the last 52 weeks:

The best place to be is the upper-right corner, with a lot of returns in play and a lot of those points won. Except… that sector is mostly empty. The women who get the most serves back–Kasatkina, Avanesyan, Sorribes Tormo–win those points at an average rate. Even that success rate is boosted a bit by the slower courts where those players tend to succeed. By contrast, the players who win the most in-play return points–Swiatek, Ostapenko, Yastremska–achieve that by missing a lot, or by being an all-time great. Even Swiatek doesn’t put an above-average number of returns in play.

With our new sense of what these numbers mean, let’s take another look at Yuan’s step forward. The limited data at hand includes five of her matches from before this week, which we can compare to the quarter-final and final from Austin. Here’s the same graph, but with points added for Yuan’s sample of previous matches (Yuan-Prev) and for the two in Austin (Yuan-ATX):

Um, yeah. Wow. There are caveats, of course: It’s just two matches, and neither Wang is a particularly stellar server. (On the other hand, Yuan’s previous opponents were middling servers as well.) If this shift is even a little bit sustainable, Yuan will no longer be just a fringe figure on tour.

Runaway momentum

While we’re extrapolating from too-small sample sizes, I’ll give you another one, one that doesn’t paint such a rosy picture for last week’s champion.

Break points go to the returner more often than return points in general, because more break points are generated against weaker servers (or by stronger returners, or both). The women currently ranked in the top 50 win 44.4% of their return points, and they convert 46.3% of break points.

Yuan, in 33 tour-level matches since this time last year, has won 44.3% of her return points, but only 43.2% of her break point chances. A gap of three percentage points (between 43% and the expected 46%) is statistical shorthand for too many missed opportunities. I checked those numbers only because the Austin champ, in both the quarters and the final, showed signs of letting momentum get away from her. Against Wang Yafan, she got broken right after securing the first set, then struggled to regain the advantage. In the final, she served for the title at 5-2 in the second set, dropping serve twice before finishing the job in a tiebreak.

As I say, these are small samples. We tend to ascribe too much importance to hot and cold streaks–they would arise even if every point were decided by a roll of the dice. (I suffered through an epic Chutes and Ladders slump yesterday, probably because of the clutch play of my four-year-old opponent.) Still, there’s some evidence that Yuan struggles under pressure, even if she overcame it several times last week.

In this context, there’s a bit of negative spin we can put on all those returns in play. I’ve written before that momentum (and clutch, and streakiness, all that stuff) is tough to measure in tennis because the structure of the sport is anti-streak. If you hit a good serve in the deuce court, you have to hit one in the ad court. Four aces in a row? Congrats, you get to do something else now–you might even have to sit down for a couple of minutes. And that’s to say nothing of your opponent’s ability to give you shots other than the ones you’re hitting well.

But against her compatriots last week, Yuan inadvertently created conditions in which streaks could take root. All those returns in play–combined with a fair number of longer points that developed on her own serve–reduced the separation between serve and return. From 5-2 in the second set of the final, Yuan’s backhand went awry, and there was little she could do to avoid it. Her own serve wasn’t imposing enough to end points quickly, and she was out of the habit of taking big cuts on return. It was easy to get into a rut.

The momentum eventually shifted, of course. Yuan won 12 of the last 15 points of her quarter-final, and in the final, she won 10 of 12 points from 5-6 in the second set to reach 6-1 in the tiebreak. She pried herself out of one pattern and immediately found a different one, one that still largely avoided short points but ended in her favor. Yuan’s conservative returning paid off on paper, but the unending string of long(ish) points may have made it harder for her to regain control on the few occasions that she lost it.

Yuan’s fellow champion last week, Katie Boulter, already stumbled at her next obstacle, losing a straight-setter yesterday in Indian Wells to Camila Giorgi. Yuan’s first test in the desert is Varvara Gracheva, a middling server who could prove susceptible to the Chinese woman’s improved game. Next up would be a tantalizing second-rounder with China’s number one, Qinwen Zheng. Zheng’s intimidating–if erratic–serve could tell us a lot more about just what Yuan is now capable of.

* * *

Subscribe to the blog to receive each new post by email:

 

Can Sebastian Baez Find Success on Hard Courts?

Sebastian Baez in Cordoba last month. Credit: jmmuguerza

Sebastian Baez is a marvel. In an era dominated by tall, all-court sluggers, the five-foot, seven-inch Argentinian has carved out a place on the circuit as a throwback clay-court specialist. Just a couple of months past his 23rd birthday, he has already won six tour-level titles and reached a new career-best ranking of 19th on the ATP computer.

The obvious comparison is Diego Schwartzman, another Argentinian on the small side who won titles and reached a French Open semi-final by grinding out victories and swinging above his weight. Schwartzman eventually cracked the top ten, but when he was Baez’s age, such a milestone looked extremely unlikely. When he turned 23, he stood outside the top 60, heading back to South America for another cycle through the continent’s late-season Challenger swing. He wouldn’t reach the top 20 for another two and half years.

If we assume Baez continues to improve throughout his mid-20s in the same way that Schwartzman did, a single-digit ranking seems achievable. He’s already 11th on tour in clay court Elo. Only a few players ahead of him on the official ranking table are younger.

The main stumbling block is the natural ceiling on dirtballers. There are far more ranking points available on hard courts than on clay, and one of the prime opportunities on the Argentinian’s favorite surface, in Madrid, plays fast because of its altitude. (Baez has competed there only once, losing in the second round last year to another sterling clay-courter, Stefanos Tsitsipas. Schwartzman never won more than two matches there, either.) For Schwartzman to gain a top-ten place, he needed more than a Roland Garros semi-final: He had recently reached indoor finals in Vienna and Cologne, and he was 14 months removed from defeating Taylor Fritz for a hard-court title in Los Cabos. Diego’s magic somehow worked on all surfaces. Even in a year when he posted outstanding results on clay, that was his only route to a single-digit ranking.

Baez owns one hard-court championship, from last year’s US Open warmup in Winston-Salem. But apart from that week, his story diverges from Schwartzman’s, with a career record on the surface of just 17-33. He has never won two completed matches at any other tour-level hard-court event. (His two third round appearances at majors were aided by retirements.) The Argentinian can be a star and a national hero without all-surface success, but surely he wants more. Can he achieve it?

Surface and speed

When I wrote about surface sensitivity a couple of weeks ago, Baez didn’t stand out as an extreme. Tsitsipas and Lorenzo Musetti were the men whose results were most dependent on slow courts. The numbers showed that Baez does better with a slower bounce, but the effect is less than half of what it is for Tsitsipas. The 23-year-old is more closely comparable in this department to Daniil Medvedev, who doesn’t like to play on clay–or eat it.

However, that analysis left out one major factor. I simply rated tournaments by the degree to which they helped servers end points quickly, regardless of surface. Indian Wells, on hard courts, came out as just barely speedier than Rome and slower than Madrid. Miami and the US Open were roughly equivalent to the Caja Magica as well.

Intuitively, there is more than one dimension to player preferences. Some men might just want more time to prepare, as could be the case with Tsitsipas and his one-handed backhand. But others–Baez among them–are much more comfortable on a certain type of surface, because of the type of bounce, the footing, or both. When we reduce surface type and speed to one variable, Baez and Medvedev come out equal. When we separate type from speed, they look very different.

This scatterplot shows 56 players on the two dimensions:

(The units are regression coefficients and essentially meaningless out of context. They do, however, show direction and magnitude of each player’s preferences.)

Among players with at least 100 tour-level matches since 2021, Baez ranks third in the degree of his preference for clay courts, behind Albert Ramos and roughly tied with Alexander Zverev. Once surface type is controlled for, he prefers faster courts. Santiago, where he won the title last week, is one of the quicker clay courts on the circuit, giving servers as many quick points as Wimbledon (really!). Rio de Janeiro, the site of his triumph the week before, is also faster than the average dirt, rating about the same as Indian Wells.

Medvedev is the exact opposite. Only Adrian Mannarino has a stronger demonstrated yen for hard courts. Once his choice of surface is secure, though, the Russian wants it as slow as possible. Only a few players (including Musetti and another slow-hard-specialist, Alex de Minaur) are so extreme.

Schwartzman–the model for a potential all-court Baez–prefers clay, and he likes all of his courts slow. His performance is even more speed-dependent than Medvedev’s, but his surface type preference isn’t nearly as strong as that of his younger countryman.

This is all rather abstract, and to some degree, it’s just a fancy way of saying that Baez struggles on hard courts. Let’s make things more concrete by looking at what happens when the Argentinian shifts to the tour’s more popular surface.

Translations

Hard-court tennis is more serve-dominated than the clay-cout variety. The typical tour regular wins, on average, 3% more service points on hard than on clay: 4% more first-serve points and 1% more second-serve points. They win 7% fewer return points. (That sounds like a paradox, since the serve and return numbers are different. The catch comes from specifying “tour regulars”–part-timers on hard courts have bigger serves than their equivalents at clay events.)

Here are the player-specific numbers for each man in the top 20 (except for Ben Shelton, who hasn’t played much on clay). The figures are ratios of each hard-court metric to the corresponding clay-court metric–serve points won, first-serve points won, and return points won–so the higher the number, the bigger the difference in favor of hard courts.

Player               SPW  1st SPW   RPW  
Ugo Humbert         1.10     1.08  0.95  
Novak Djokovic      1.09     1.11  0.91  
Alex de Minaur      1.08     1.08  0.99  
Daniil Medvedev     1.06     1.07  0.98  
Jannik Sinner       1.06     1.08  0.95  
Tommy Paul          1.06     1.08  1.08  
Grigor Dimitrov     1.06     1.04  0.95  
Holger Rune         1.05     1.06  0.92  
Taylor Fritz        1.05     1.09  0.93    
Alexander Zverev    1.05     1.03  0.89

Player               SPW  1st SPW   RPW  
Alexander Bublik    1.05     1.04  1.04  
Karen Khachanov     1.05     1.09  0.96  
Andrey Rublev       1.05     1.05  0.94  
Hubert Hurkacz      1.04     1.02  1.00  
Frances Tiafoe      1.03     1.05  0.95  
- ATP Regular -     1.03     1.04  0.93  
Carlos Alcaraz      1.02     1.02  0.92  
Stefanos Tsitsipas  1.02     1.03  0.89  
Casper Ruud         1.01     1.04  0.91  
Sebastian Baez      0.94     0.96  0.85

Baez is… different. Everyone in the top 20 wins more serve points on hard courts than on clay except for him. Only a few other men on tour have the same “backwards” split, and only Federico Coria is close to Baez in the degree of his weaker hard-court service performance. What costs the Argentinian even more is how his return numbers suffer away from clay. Almost everyone wins fewer return points on hard, but Baez takes the cake here too.

Perhaps needless to say, there’s no way that this can work. Baez wins about 62% of service points on clay, a respectable number and an impressive one for someone his size, but still below the average of a top-50 player on the surface. To win even fewer on hard suggests that he would struggle even at Challenger events. At Winston-Salem last August, Baez won 63.5% of his serve points and over 43% on return. That’s a combination that will win matches; he just hasn’t provided any evidence that he can pull it off once he crosses back out of North Carolina.

Growth rate

The one reason for optimism is that Baez is young, inexperienced on surfaces other than clay. Like Schwartzman, he grew up playing on dirt, and he rose through the rankings by winning South American Challengers, then picking up victories on the continent’s Golden Swing. Maybe there’s a necessary transition period?

Here are the same ratios as above, now by season for our two Argentinian heroes:

Player  Year   SPW  1st SPW   RPW  
Diego   2015  1.01     0.99  1.01  
Diego   2016  1.04     1.07  0.94  
Diego   2017  1.08     1.09  0.91  
Diego   2018  1.03     1.03  0.89  
Diego   2019  1.08     1.09  0.94  
Diego   2020  1.03     1.03  0.85  
Diego   2021  1.02     1.03  0.95  
Diego   2022  1.01     1.04  0.89  
Diego   2023  1.09     1.08  0.88  
                                   
Player  Year   SPW  1st SPW   RPW  
Baez    2022  0.91     0.94  0.82  
Baez    2023  0.96     0.99  0.88

Baez did close the gap between his hard-court and clay-court performances in his second year on tour. But he still shows a more marked surface preference than Schwartzman ever did. As soon as Diego arrived on tour, he was able to win more service points on hard courts–roughly the same ratio as the typical tour regular. Baez isn’t even close. Schwartzman had to retool his game to succeed on hard courts, and Baez will need to do so even more.

The 23-year-old truly is a throwback, an undersized grinder who spins in his serves, plays defense, and constructs points. It’s a joy to watch, and the package makes him one of the best players on tour for the 14 weeks or so each year when there are top-level clay events on offer. It doesn’t, however, work so well when there’s no dirt to kick out of his cleats. Fortunately Baez is young, and he has many years left to figure it out. He’ll need to.

* * *

Subscribe to the blog to receive each new post by email:

 

Katie Boulter’s Game of Patience

Katie Boulter in 2021. Credit: Chris Czermak

You can be forgiven if you didn’t have Katie Boulter on your radar going into the 2024 season. Her career-best ranking in the top 60 was a bit misleading, stemming largely from a debut title on the grass at Nottingham, where she picked up the championship without facing a single top-130 player. Nothing she can do about that, of course, but when it came to things she could control, the results were not always so encouraging. She wrapped up 2023, at 27 years of age, with a career total of just 25 hard-court victories.

Since then, it’s been a whole new Katie. She opened her campaign with an upset of 5th-ranked Jessica Pegula at the United Cup, and counting qualifying, she has won at least one match at six straight events. To solidify her new status, she won the title in San Diego last week, knocking out four seeded players in the process. Nothing cheap here: All five of her opponents were ranked in the top 36, and the weakest among them–Lesia Tsurenko–had won each of their three previous meetings.

After years in the ITF wilderness, relying on British grass-season wild cards for tour-level appearances, Boulter has earned a place in the WTA top 30. Thanks to the giant-killing in Southern California, her Elo rating backs it up, placing her 28th on tour, 26th on hard courts. The Brit has always had a first serve and forehand that made it possible to dream big. It has just been a matter of harnessing the big weapons and filling out her game with complementary parts that wouldn’t leave her exposed.

The results from San Diego suggest that she has finally done so. Commentators like to talk about the importance of playing “within” oneself, waiting for opportunities instead of swinging for winners when none are on offer. Boulter hasn’t always done that, and she has the unforced error totals to prove it. She found a better balance against last week’s barrage of top-40 foes, playing a bit more conservatively and cutting down mistakes without sacrificing too many winners. Now, she’s on everyone’s radar.

Katie bolt the door

Boulter ascended through the ranks with what might best be described as low-percentage tennis. In her 100+ matches on tour, she has landed just 57% of her first serves, racking up more double faults than aces. 13% of her groundstrokes are unforced errors, well above tour average. Her typical return point lasts just barely three strokes.

In twelve matches logged by the Match Charting Project before last week’s run in San Diego, a mixed bag ranging from ITFs in 2017 to her final-round victory over Jodie Burrage in Nottingham last year, her Rally Aggression Score worked out to 84, putting her in the same range as free swingers such as Caroline Garcia and Camila Giorgi. Against Burrage, her Rally Aggression Score was 267, a remarkable figure for a stat that I initially scaled so that it would max out around 100. Just about every possible shot–plus a few impossible ones–was a winner or unforced error. The average point in that match lasted just 2.9 shots.

It’s possible to win with numbers like these–just ask Aryna Sabalenka, Petra Kvitova, or Jelena Ostapenko. But the margins are slim. It’s particularly tough to thread the needle while making as few first serves as Boulter does. Surprisingly, she struggled on that front in San Diego, making just 54% of her first deliveries for the week, including a mere 51% against Emma Navarro in the semi-final. When only one-quarter of total points begin with your best shot, you can’t risk missing so much with the rest of your arsenal.

The Brit’s most effective step forward, especially against Kostyuk in Sunday’s final, was to keep herself in more return points. She has traditionally swung big on return, ending 11% of second-serve points with a return winner or forced error, and even finishing 6% of first-serve points that way. She didn’t sustain those numbers in the final, but the tradeoff was worth it. In those previous 12 charted matches, she put just 60% of first-serve returns in play, compared to a tour average closer to 75%. Facing Navarro, she kept the point alive on 65% of first serve returns; against Kostyuk, she put the ball back in play 79% of the time.

The result, more or less by definition, was longer return points. While the Burrage match was extreme, it is not uncommon for Boulter to average in the neighborhood of three strokes per point on return–still in Ostapenko territory. The San Diego semi was a wholly different animal, with her average return point lasting 4.5 shots. In the final, it was 4.1 shots. Such a radical shift would be a bad sign for many big hitters: Ostapenko and her ilk end points early because that’s the way they want to play. Yet Boulter thrived on her newfound patience.

The 27-year-old won 47% of her return points in San Diego, five percentage points better than her tour-level average and about the same as a typical performance from Pegula or Coco Gauff. On Sunday against Kostyuk, Boulter played 81 return points and won 40 of them.

Winners, slightly delayed

Even though she did not smack as many return winners as usual over the weekend, Boulter still won plenty of points from the baseline. She just took fewer risks in the process. Excluding aces and double faults, here’s a top-level comparison of the frequency with which she hit winners (plus forced errors) and unforced errors in her last two matches, compared with her previous charted matches and WTA average:

Match(es)    W+FE  UFE  
vs Kostyuk    14%   9%  
vs Navarro    19%   8%  
Previous      16%  13%  
WTA Average   12%  10%

The Navarro match was an unalloyed triumph, as you might expect from the 6-3, 6-1 scoreline. But even the Kostyuk numbers point to a major step forward. It’s not easy to cut down unforced errors from one side of tour average to the other, especially against someone like the Ukrainian, who feeds opponents an ever-shifting mix of speeds and depths. In the past, the Brit might have lost her rhythm and gone on an error spree. Instead, she was even steadier. On 28 key return points–game point, deuce, or break point–Boulter committed just one unforced error.

Facing women without the weapons to quickly end points themselves, Boulter discovered that a winner on the fourth or fifth shot of the point is just as effective, and less risky, than a big swing on the second or third shot. In her previous charted matches, she won about 49% of points that lasted four to six shots. Against Kostyuk, she won 76%, dictating play the way she has always preferred to do, just one or two shots later.

Presumably, it won’t always be quite this easy. Boulter won’t keep her unforced error rate in single digits forevermore; more aggressive opponents will tempt her into playing her old game. (Though the Brit did straight-set Donna Vekic in the quarters.) Still, she appears to have discovered new capabilities, seven years after her first appearance at Wimbledon. This year, she’ll likely return to the All-England Club as a seeded player, with all the expectations and pressure that entails. A decade into her pro tennis career, Boulter has earned herself a lot more attention.

* * *

Subscribe to the blog to receive each new post by email:

 

Alex de Minaur’s Adequate Inaccuracy

Alex de Minaur at the 2024 Australian Open. (Getty Images: Julian Finney)

Last week, Tennis Insights posted a graphic showing the average first serve speed and accuracy–distance from the nearest line–for the ATP top 20. There’s a ton of fascinating data packed into one image.

Hubert Hurkacz is fast and accurate, Novak Djokovic is nearly as precise, and Adrian Mannarino defies logic as always. The most noteworthy outlier here, especially just after his run to the Rotterdam final, was Alex de Minaur. The Australian gets plenty of pop on his first serve, hitting them faster than tour average, if slower than most of the other men in the top 20. This comes at a cost, though. As one of the shortest guys among the elite, he doesn’t hit the lines. He’s by far the least accurate server in this group:

Precision is great: It’s certainly working for Hurkacz and Djokovic. But everything is a tradeoff. Any pro player could hit more lines if there was no reason to serve hard. Or vice versa: If the goal was simply to light up the radar gun, these guys could add miles per hour by aiming at the middle of the box. Standing a modest six feet tall, De Minaur is even more constrained than his typical peer. No technical tweak is likely to move him into Hurkacz territory. He might make small improvements or swap some speed for more accuracy.

Small gains would be enough, too. De Minaur wins fewer first-serve points than the average top-50 player, but in the last 52 weeks, he has outpaced Carlos Alcaraz, Holger Rune, and Casper Ruud. He trails Alexander Zverev by about one percentage point. This isn’t Sebastian Baez (or even Mannarino) we’re talking about. Whatever the cost of de Minaur’s inaccuracy, he’s able to overcome it. It’s just a matter of what gains he could reap by making returners work a bit harder.

Here’s the question, then: How much does accuracy matter?

Speed first

For this group of players over the last 52 weeks, speed is by far the most important factor in first-serve success. Speed alone–ignoring accuracy or anything else–explains 72% of the variation in first-serve points won. Accuracy alone accounts for 43%. (The players who are good at one thing are often good at others, so most of those 72% and 43% overlap.) 43% might sound like a lot, but isn’t that far ahead of something as fundamental as height, which explains 33% of the variation.

Surprisingly, precision is even less critical when it comes to unreturnable first serves. Using unreturned serve counts from Match Charting Project data, accuracy explains just 30% of the variation in point-ending first serves, less than we could predict from height alone. (Speed alone explains 60% of the variation in unreturned serves.) I would have expected that accuracy would play a big part in aces and other unreturned serves, since a ball close to the line is that much harder to get a racket on. But while precision may increase the odds of any individual serve going untouched, average precision isn’t associated with untouchable serving.

The story is the same for any metric associated with first-serve success. Speed matters most. There’s immense overlap between the factors I’ve discussed: Taller players find it easier to hit the corners, and all else equal, they take less of a risk by hitting bigger. There is probably some value of height that isn’t captured by speed or accuracy, such as the ability to put more spin on the ball, but the main benefit shows up on the radar gun.

To tease out the impact of each variable, I ran a regression that predicts first-serve points won based on speed, accuracy, and height. The results should be taken with an enormous grain of salt, since we’re looking at just 20 players, some of them the game’s most outrageous outliers. Still, the findings are plausible:

  • Speed: Each additional mile per hour translates to an improvement of 0.43 percentage points in first-serve points won. (1 kph: +0.27 first-serve points won)
  • Accuracy: Decreasing distance from the line by 1 cm results in an improvement of 0.2 percentage points in first-serve points won.
  • Height: At least for these twenty players, the value of height is entirely captured by speed and accuracy. The margin of error for the height coefficient spans both positive and negative values. It is unlikely that height is a negative, though I suppose it’s possible, if speed and accuracy capture the height advantage on the serve itself, and height is a handicap on points that develop into rallies. Either way, the impact is minor, if it exists at all.

Approximately, then, one additional mile per hour is worth the same as two centimeters of accuracy. The height of the graph–110 to 130 mph–represents a variation of nearly 9 percentage points of first-serve points won. The width–70 to 52cm–represents a range of 3.6 percentage points. Broadly speaking, speed remains more important than accuracy, though a particular player might find it easier to improve precision than power.

Just one example of what the numbers are telling us: De Minaur has won 72.8% of his first-serve points over the last year, compared to the top-ten average of 75.3%. If this model were to hold true–a big if, as we’ll discuss shortly–that’s a gap he could close by improving precision by about 12 cm, to a tick better than tour average.

Drowning in caveats

For every question we answer, we’re rewarded with ten more questions.

I’m most interested in the choices that individual players could conceivably make, and the analysis so far offers only hints to that end. For this group of servers, we can say that a player who serves faster will win more points than his slower-serving peers. But we don’t know whether a specific player, if he was able to juice his serve by a mile or two per hour, would enjoy the same benefits. Hitting harder, or placing the ball more accuracy, is better, but by how much?

(I dug into the speed question way back in 2011 and found that one additional mile per hour–for the same player–was worth 0.2 percentage points. More recently, I found that for Serena Williams, an additional mile per hour was worth 0.5 percentage points. One of these days I’ll revisit the initial study with the benefit of many more years of data and perhaps a bit more wisdom.)

De Minaur was unusually precise in Rotterdam. Another Tennis Insights graphic indicates that his accuracy improved to about 55 cm for the week, an enormous gain of 15 cm from his usual rate, even more remarkable because his average speed was a bit quicker as well. (Playing indoors probably helped.) The model suggests that 15 cm is worth three percentage points. His boost of two miles per hour should have been worth nearly one more percentage point itself. Yet he won “only” 73.9% of his first-serve points–about one percentage point better than his non-Rotterdam average.

It’s just one week, so it isn’t worth fretting too much over the discrepancy. Still, it illustrates the value of the data we don’t have. (By “we,” I mean outsiders relying on public information. The data exists.) If we knew de Minaur’s accuracy and speed for every match, we could figure out their value to him specifically. Perhaps an uptick of one mile per hour is worth 0.43 percentage points only if you start serving like the players who serve faster–guys who are generally taller and can put more slice or kick on the ball. Those weapons aren’t available to the Aussie, so a marginal mile per hour may be less valuable. For him, accuracy might have a bigger payoff–relative to speed–than it does for other players. We just don’t know.

Sill, we’ve extracted a bit of understanding from the data. We’ve seen that accuracy translates into more first-serve points won, and we have a general idea of how many. De Minaur showed himself capable of hitting the lines as precisely as Andrey Rublev or Grigor Dimitrov, at least under a roof for one week. Just half that improvement, if he could sustain it–even if he didn’t get the full gains predicted by the model–would shore up a mediocre part of his game and lay the groundwork for a longer stay in the top ten.

* * *

Subscribe to the blog to receive each new post by email:

 

Surface Sensitivity and Ugo Humbert’s Serve

Ugo Humbert in 2023. Credit: Hameltion

Let’s start off with a couple of puzzles. I realize they aren’t the sort of things that keep most of you up at night, but they were odd enough to drive me to a flurry of coding, data analysis, and now blog writing.

On Wednesday, Ugo Humbert lost his first-round match in Rotterdam to Emil Ruusuvuori. It marked an unceremonious end to a hot streak for Humbert: He not only won the title in Marseille last week–launching himself into the Elo top ten–but he strung together 31 consecutive holds. 1,000 kilometers north, on a different indoor hard court, he got broken twice by a man ranked outside the top 50.

That’s the first puzzle: Why did the Frenchman lose? Again, it’s not that odd, as my Elo ratings gave Ruusuvuori a one-in-three shot to pull the upset. But it’s a match that Humbert should have won.

Head-scratcher number two: Why does Humbert always lose to Ruusuvuori? Wednesday’s decision marked their fifth meeting, and the Finn is undefeated. While the outcome is always close–Rotterdam was their fourth deciding set, and the other match went to two tiebreaks–the results are starting to get boring. Ruusuvuori is a solid player, and he is consistently able to blunt the Frenchman’s serve. But five in a row?

The answer to both mysteries is the same, and it’s more satisfying than I expected. Rotterdam is unusually slow for a hard court, especially indoors. Like most (or perhaps all) of the previous Humbert-Ruusuvuori venues, it plays slower than tour average. Just as important, Humbert’s game is unusually sensitive to surface speed. While that isn’t always true of big servers, he stands out as a fast-court specialist. We couldn’t have confidently predicted a Finnish upset, but we could have guessed that the Marseille champion would find this week’s tournament tougher going.

Rotterdam, it’s slow

The last time I published surface speed numbers, in late 2019, Rotterdam rated as the slowest indoor hard court on tour. Adjusting for the mix of players at the event, there were 10% fewer aces at the tournament than expected. It was a sharp decline from 2017 and 2018, when the venue sported more typically speedy indoor conditions.

Since then, the results have remained similar. Last year, the rate was 5% lower than expected, roughly tied with Stockholm as the slowest indoor surface on tour. Marseille, by contrast, gave players 12% more aces than usual.

There are limitations to using aces as a proxy for surface speed; I use aces because it’s the most relevant data that is widely available. Still, while you can quibble about the methodology or about a specific tournament’s place on the list, the overall rank order seems about right. Aces–adjusted for each event’s field–tell you much of the story.

With a growing mass of Match Charting Project data, we can do a little better. We have shot-by-shot logs for over one thousand matches since 2021. To compare conditions, I used my Serve Impact metric, which estimates how many points a player wins, directly or indirectly, because of his serve. It counts aces, other unreturned serves, and a fraction of the service points that take longer to decide. Depending on your motivation in measuring court speed, this isn’t perfect either: It doesn’t directly tell you anything about bounce height, for instance. But if you want to know what sort of players a tournament favors, Serve Impact gets you close.

By this more sophisticated metric, Rotterdam is… still slow. The venue takes away 4% of the points a player typically earns from his serve. Marseille and Montpellier each swing 7% in the other direction, Stockholm and Vienna provide a modest 3% boost, and Basel adds 8% to the server’s punch. With the exception of the short-lived tour stop in Gijon, Rotterdam has been the slowest indoor hard court of the 2020s. Even the clay in Lyon plays faster.

Here are the Serve Impact adjustments for the tournaments best represented in the dataset. Higher numbers mean faster conditions with more points decided based on the serve:

Tournament            ServeImpact  
Stuttgart                    1.29  
NextGen Finals               1.20  
Tour Finals                  1.16  
Wimbledon                    1.11  
Shanghai Masters             1.11  
Halle                        1.10  
Queen's Club                 1.08  
Basel                        1.08  
Washington                   1.08  
Dubai                        1.07  
                                   
Tournament            ServeImpact  
Antwerp                      1.05  
Gstaad                       1.05  
Australian Open              1.04  
Davis Cup Finals             1.04  
Cincinnati Masters           1.04  
Paris Masters                1.03  
Vienna                       1.03  
Miami Masters                1.02  
Madrid Masters               1.01  
US Open                      1.01  
                                   
Tournament            ServeImpact  
Canada Masters               1.00  
Rotterdam                    0.96  
Indian Wells Masters         0.95  
Rome Masters                 0.92  
Acapulco                     0.87  
Barcelona                    0.87  
Roland Garros                0.83  
Monte Carlo Masters          0.83 

Average Serve Impact is around 34%, so the 4% hit in Rotterdam knocks that down to about 32.6%. Humbert has an above-average serve, so the slow-court penalty is greater still. He isn’t going to win any awards for rallying prowess, especially against someone as sturdy as Ruusuvuori, so the points that he doesn’t secure with his serve will disproportionately go against him.

The first three meetings in the Humbert-Ruusuvuori head-to-head were on clay, at Roland Garros, Madrid, and Rome. The fourth came on grass, at ‘s-Hertogenbosch. It rates a bit faster from 2021-23 than Halle or Queen’s Club by the Serve Impact metric, though it rated as the slowest grass court on tour last year by my older ace-rate algorithm. Maybe it was less server-friendly in 2023, just in time for Humbert to be flummoxed once again.

Surface sensitivity

We tend to take for granted that players are suited to conditions in predictable ways. Big servers like fast surfaces, right? Broadly speaking, yes, but it’s not a hard-and-fast rule. Bounce height makes a difference, footwork matters, and some players are just more comfortable on some surfaces than others.

Armed with surface speed ratings, this is something we can test. If a player is particularly sensitive to conditions, each tournament’s Serve Impact rating should have a predictable influence on his match outcomes. I tried that for all tour regulars, controlling for player strength by using overall Elo ratings at the time of each match.

The resulting numbers are an abstraction on top of an abstraction, so they’re a bit difficult to get your head around. I’ve tried to simplify matters by rendering them in terms of Elo points. A player who is very sensitive to surface and does better on hard courts is, effectively, a better player in faster conditions. The ‘Sensitivity’ numbers given here are the benefit–denominated in Elo points–of each single percentage point that a surface is faster than average. For players who like it slow, negative numbers express the same idea, the Elo-point advantage of a one-percentage-point slowdown.

Here is the list of all players with at least 100 tour-level matches since 2021, plus Rafael Nadal:

Player                       Sensitivity  
Tallon Griekspoor                   11.1  
Ugo Humbert                          9.5  
Richard Gasquet                      9.1  
Novak Djokovic                       8.7  
Adrian Mannarino                     7.9  
Sebastian Korda                      4.9  
Jordan Thompson                      4.3  
Matteo Berrettini                    4.0  
Aslan Karatsev                       3.6  
Tommy Paul                           3.4  
Marcos Giron                         2.9  
Marton Fucsovics                     2.9  
Marin Cilic                          2.6  
Felix Auger-Aliassime                2.1  
Hubert Hurkacz                       1.7  
                                          
Player                       Sensitivity  
Frances Tiafoe                       1.6  
Carlos Alcaraz                       1.4  
Emil Ruusuvuori                      1.3  
Brandon Nakashima                    1.3  
Cristian Garin                       0.6  
Alexander Zverev                     0.5  
Alexander Bublik                     0.5  
Ilya Ivashka                         0.0  
Arthur Rinderknech                  -0.1  
Taylor Fritz                        -0.3  
Jan Lennard Struff                  -0.3  
Lorenzo Sonego                      -0.4  
Mackenzie Mcdonald                  -0.5  
Andy Murray                         -0.9  
Grigor Dimitrov                     -1.1  
                                          
Player                       Sensitivity  
Roberto Bautista Agut               -1.2  
Alex de Minaur                      -1.2  
Karen Khachanov                     -1.4  
Jannik Sinner                       -1.4  
Yoshihito Nishioka                  -1.5  
Miomir Kecmanovic                   -1.9  
Andrey Rublev                       -2.2  
Daniel Evans                        -2.2  
Cameron Norrie                      -2.5  
Holger Rune                         -2.9  
Roberto Carballes Baena             -3.0  
Botic van de Zandschulp             -3.1  
Daniil Medvedev                     -3.4  
Denis Shapovalov                    -3.5  
Sebastian Baez                      -3.7  
                                          
Player                       Sensitivity  
Laslo Djere                         -4.1  
Dusan Lajovic                       -4.1  
Pablo Carreno Busta                 -4.4  
Jaume Munar                         -4.6  
Fabio Fognini                       -4.8  
Nikoloz Basilashvili                -4.9  
Casper Ruud                         -5.0  
Diego Schwartzman                   -5.4  
Francisco Cerundolo                 -5.9  
Alexei Popyrin                      -6.4  
Albert Ramos                        -6.8  
Rafael Nadal                        -9.9  
Alejandro Davidovich Fokina        -10.1  
Stefanos Tsitsipas                 -10.2  
Lorenzo Musetti                    -11.2 

There’s Ugo! He’s not quite as surface sensitive as Tallon Griekspoor, but a couple of points is within the margin of error. A sensitivity rating of 9.5 means that Humbert is about 100 Elo points worse in Rotterdam than he is Marseille, as long as I’ve accurately estimated the server-friendliness of the respective playing conditions. Ruusuvuori may also like it faster, but only marginally so; he’s effectively neutral.

Keen-eyed readers may have noted that I earlier referred to “overall” Elo. I’m not using surface-specific Elo ratings here, because I don’t want to adjust for surface twice. Surface-specific ratings already capture some of this: Humbert’s hElo (for hard courts) is 120 points higher than his cElo (for clay courts), which tallies reasonably well with these more fine-grained distinctions. What hElo and cElo can’t tell us, though, is how much his (or anyone else’s) performance will vary on the same surface, depending on the conditions at each specific venue.

It’s easy to get lost in the weeds of Elo-based forecasting calculations, but it’s important to remember they are just tools to help measure a real-world phenomenon. Not every big server is equally at sea on clay; some dirtballers are less dependent on slow conditions than others. Small differences in surface speed are, for most matchups, a minor consideration. But for some players, conditions matter a lot. Ugo Humbert likes his surfaces fast, as much as almost anyone else on tour. In Rotterdam, the conditions did not cooperate.

* * *

Subscribe to the blog to receive each new post by email:

 

Welcome to the Show, Luciano Darderi

Luciano Darderi in 2023. Credit: jmmuguerza

Italian tennis hardly needs any more prospects, but Luciano Darderi has announced himself as yet another young player to watch. The Argentinian-born right-hander turns 22 today, three days after securing his debut ATP title. He came through qualifying in Cordoba, and in just his third appearance in a tour-level main draw, knocked out the 2nd, 4th, and 7th seeds en route to the championship.

Darderi is a supercharged clay courter, comfortable on dirt yet possessing a serve and forehand that will play on faster surfaces. He cracked 25 aces in the Cordoba main draw, plus another 11 in qualifying. On Sunday, fellow qualifier Facundo Bagnis got barely half of Darderi’s first serves back in play. Against Sebastian Baez in the semi-finals, the Italian ended 22 points with a forehand winner or forced error and, as we will see, held his own from the baseline against one of the game’s most stubborn defenders.

Though the magnitude of Darderi’s breakthrough came out of nowhere, he has been inching toward a double-digit ranking for some time. He reached 13 Challenger quarter-finals last year, advancing to three finals and collecting a pair of titles. He finished the year ranked 128th and gained 60 places with the victory in Cordoba, ensuring he’ll have plenty more chances to prove his mettle on tour.

He hasn’t hesitated to take advantage, dropping just three games in beating Mariano Navone in Buenos Aires yesterday. The victory extended the Italian’s winning streak to eight and shows just how fast he is developing, having lost to Navone in a bruising Challenger final just a few months ago.

It won’t always be so smooth for Darderi: The hard-court skew of the top level of the circuit may not prove hospitable to a youngster who has played 84% of his career matches on clay. Even with the right weapons in hand, it will take some time to become more than just a dark horse on the Golden Swing. But that’s all in the future: Darderi’s 22nd birthday is an ideal opportunity to dig into the upsets that lifted him from Challenger warrior to the top 100.

Bullying the little guy

The defining win of the Italian’s week in Cordoba was the semi-final. Baez struggled at the end of 2023, but he is always a tough out on clay, especially coming off a third-set-tiebreak victory in Davis Cup. At just five-feet, seven-inches tall, the Argentinian relies on speed and defense, neutralizing the weapons of larger men. It doesn’t always work–his serve puts him at an immediate disadvantage, and he can become overly aggressive and error-prone to compensate–but he doesn’t give much away.

Despite his size, Baez doesn’t mind going toe-to-toe with an opponent’s best shot. In 19 clay-court matches tracked by the Match Charting Project since the beginning of 2022, Baez’s opponents have hit forehands–excluding service returns–as 61% of their baseline shots, compared to a tour-wide clay-court average of 55%. Thomaz Bellucci found the forehand 72% of the time against the Argentinian; Tallon Griekspoor clocked in at 71%.

Both lost. No matter what the shot, if you find yourself in a rally with Baez, your odds aren’t good. When you hit a forehand after the service return, your chances of winning the point are 45%; with a backhand, your chances are 44%. (Tour averages on clay are 53% and 47%, respectively.) Some individual cases are downright comical. In the 2022 Bastad quarter-finals, Dominic Thiem won just 27% of points when he hit a forehand. When the two men met again in the Kitzbuhel final last year, Thiem relied a bit more on his backhand. Alas, he won only 14% of points when he hit one of those.

Darderi ran around a few backhands to find his bigger weapon, but he generally refused to take the bait. He waited for his spots to attack one of the toughest men on tour to be patient against. This table details the results he got from his forehands and backhands in the semi-final:

                   FH/GS  FH W%  FH Wnr%  FH UFE%  
Darderi vs Baez    55.4%  50.6%    12.2%     8.5%  
Average vs Baez    60.6%  45.2%    10.4%    12.0%  
                                                   
                   BH/GS  BH W%  BH Wnr%  BH UFE%  
Darderi vs Baez    44.6%  48.5%     6.1%     6.8%  
Average vs Baez    39.4%  43.8%     6.3%    10.3%

The Italian hit fewer forehands than the usual Baez opponent, and it won him more points, in part thanks to hitting winners at a higher rate and coughing up fewer unforced errors. His backhand numbers were favorable as well, perhaps in part because he set up for backhands in places where other opponents would go for an inside-out forehand. He was particularly stingy with free points on that wing.

Despite possessing the bigger gun, Darderi let his opponent make the mistakes. Baez obliged, piling up 32 unforced errors, including an uncharacteristic 11% of his backhands. Winning percentages of 50.6% and 48.5% hardly make for good headlines, but coupled with a big serve, they are enough to beat Baez. Few players on tour have been able to manage the same.

Tailored attack

The classic clay-court baseline weapon is the inside-out forehand, a salvo that might not end the point, but will pull the opponent out of position and leave the court open for a finishing blow. Darderi can win matches with that shot, as he did in the final against Bagnis. His left-handed opponent kept sending balls to his backhand corner, and the Italian ran around a lot of them. More than half of Darderi’s forehands in the final were inside-out, and he won the point 78% of the time he hit one. The match wasn’t close.

As we’ve seen, though, manufacturing forehands against Baez is a trap. The Argentinian can blunt the angle and absorb the pace, and meanwhile, his opponent is out of position. When Thiem had his terrible day in Bastad, he hit 62 inside-out forehands, only 16 of them in points that he won. (He typically wins more than half, as does the tour as a whole.) Whether by preparation or intuition, Darderi took those chances much less often, and far less frequently than he would against Bagnis. Just one in six of his forehands were of the inside-out variety, and he won just shy of half those points.

Instead, with Baez accustomed to playing defense on the backhand side, Darderi attacked to the forehand. While he didn’t go crosscourt particularly often, he hit hard when he did. 22% of his crosscourt forehands ended the point in his favor with a winner or forced error. That shot can be a slightly favorable play against Baez–opponents win 47% of those points, compared to 45% for forehands overall–but only Nicolas Jarry has cleaned up against Baez in this category the way that Darderi did. It’s way too early to draw any conclusions about how the Italian’s game will fare on tour, but when you share the top of a forehand leaderboard with Jarry, you’re doing something right.

A big serve and a forehand isn’t enough: Nearly everybody has those, even if Darderi’s forehand has a bit of extra mojo. Upsetting the forehand-neutralizing Baez, especially in between victories against less complicated opponents, is a sign that the Italian has resources between his ears as well. Every week, it seems, Italian tennis looks a little bit better.

* * *

Subscribe to the blog to receive each new post by email:

 

Elena Rybakina and the Value of Average

Also today: Ugo Humbert in the (Elo) top ten; South American Davis Cup hard courts

Elena Rybakina at the 2023 US Open. Credit: Hameltion

Never underestimate average. Establishing oneself on the top level of the pro tennis circuit is extraordinarily difficult; proving that any particular skill is average among one’s tour-level peers is even harder. Most players are better than the norm in some categories, worse in others. Anyone who can beat the middle of the pack in every department is virtually guaranteed to be a superstar.

Average is Elena Rybakina’s secret weapon. You probably didn’t know she needed one, because she has a very effective, very evident non-secret weapon: an unreadable bullet of a first serve. In the last year, over 43% of her first serves have gone unreturned. No one else on tour comes within three percentage points of that, and only five other women top 35%. On a good day, the serve can put a match out of reach nearly on its own. When she faced Aryna Sabalenka in Beijing last fall, 65% of her first serves didn’t come back. Most women barely manage to win that many first serve points, let alone decide them with one stroke.

I’ll come back to the serve in a moment, because it is so remarkable, and it would be strange to talk about Rybakina without discussing it. But what makes her a contender every week–not to mention a champion in Abu Dhabi yesterday–is the way that the rest of her game doesn’t hold her back. Among the other women who end points with more than 35% of their first serves, you’ll find a long list of weaknesses. Qinwen Zheng doesn’t put nearly enough of them in the box. Donna Vekic and Caroline Garcia struggle to break serve. Liudmila Samsonova doesn’t break much, either, and her mistakes come in excruciating, match-endangering bunches.

Lopsided player profiles make sense. Only a few people have the combination of natural gifts and discipline to develop a dominant serve. Tennis skills are correlated, but not perfectly so. Someone who serves like Vekic can often learn good-enough groundstrokes and secondary shots. But players with one standout skill are unlikely to be solid across the board. Just because someone is top ten in the world in one category, why would we expect them to rank in the top 100 by a different measure?

Rybakina has reached the top–or close, anyway–by coupling a world-class serve with a set of skills that lacks defects. (You can nitpick her footwork or technique, but none of that holds her back when it comes to winning enough points.) After we review the devastation wrought by her serve, we’ll see just how average she otherwise is, and why that wins her so many matches.

First serves first

I’ve already given you the headline number: Since this time last year, 43.4% of Rybakina’s first serves haven’t come back. That’s one percentage point better than Serena Williams’s career rate. Serena’s numbers are based on matches logged by the Match Charting Project, a non-random sample skewed toward high-profile contests against strong opponents, so I’m not ready to say outright that Rybakina is serving better than Serena. But I’m not not saying that–we’re within the margin of error.

Some back-of-the-envelope math shows what kind of gains a player can reap from the best first serve in the game. Rybakina makes about 60% of her first serves–lower than average, but probably worth the trade-off. (And improving–we’ll talk about that in a bit.) When the serve does come back, she wins about half of points, roughly typical for tour players. All told, 43% of her serve points are first-serve points won. Tack on about half of her second serve points–she wins 48% of those, better than average but not by a wide margin–and we end up with her win rate of 62.5% of serve points–fourth-best on tour.

Put another way: We combine one world-class number (unreturned first serves) with a below-average figure (first serves in), one average number (success rate when the serve come back), and one more that was slightly better than average (second-serve points won). The result is an overall success rate that trails only those of Iga Swiatek, Sabalenka, and Garcia. That, in case you ever doubted the value of an untouchable first serve, is the impact of one very good number.

The key to Rybakina’s first serve–apart from blinding speed–is its unreadability. She must lead the tour in fewest returner steps per ace, a stat I dreamed up while watching the Abu Dhabi semi-final on Saturday. Samsonova seemed to stand bolted to the ground, watching one serve after another dart past her. After one business-as-usual ace out wide, Samsonova even offered a little racket-clap of appreciation, an unusual gesture for such a routine occurrence.

In addition to the deceptiveness of a nearly identical toss and service motion, Rybakina is effective in every direction. There’s no way for an opponent to cheat to one side, hoping to get an edge on a delivery in that corner of the box. Here are Elena’s rates of unreturned first serves and total points won in each corner of the two service boxes:

Direction   Unret%  Won%  
Deuce-Wide     36%   69%  
Deuce-T        45%   75%  
Ad-T           37%   70%  
Ad-Wide        42%   74%

The average player ends points with their first serve between 20% and 25% of the time and wins 60% of their first serve points. Rybakina obliterates those numbers in every direction. If there’s a strategy to be exploited, it’s that returners ought to lean toward their forehand, because if the serve comes to their backhand, they don’t have a chance anyway.

The scariest thing for the rest of the tour is that the 24-year-old’s biggest weapon may be getting even bigger. Her 43.4% rate of unreturned first serves in the last 52 weeks compares favorably to a career clip of 38.2%. Against Samsonova on Saturday, over 41% of all serves didn’t come back, better than Rybakina managed in any of their four previous meetings.

She may be getting savvier, too. One of the dangers of a game built around a single weapon is that certain players might be able to neutralize it. Daria Kasatkina, Elena’s opponent in yesterday’s final, is just such an opponent, a resourceful defender and a first-class mover. When the two women played a three-and-a-half-hour epic in Montreal last summer, Kasatkina put three-quarters of first serves back in play, something that few women on tour could manage and one of the main reasons the match stretched so long. Rybakina survived, but she was broken ten times.

Yesterday, Kasatkina was as pesky as ever, getting almost as many balls back as she did in Montreal. But Rybakina took fewer chances with her first strike, perhaps as much to counter the wind as to adjust for her opponent. Whatever the reason, Elena made three-quarters of her first serves. She had never landed more than 61% against Kasatkina.

The Abu Dhabi final was an exaggerated example of a longer-term trend. Somehow, Rybakina is making way more first serves than ever before, sacrificing no aces and only a fraction of first-serve points won. The overall results speak for themselves:

Year    1stIn%  1st W%   Ace%   SPW%  
2024     66.8%   70.9%  10.3%  64.8%  
2023     56.8%   73.6%  10.5%  62.8%  
Career   57.8%   71.1%   8.4%  62.0%

It’s not a perfect comparison, because the entire 2024 season so far has been on hard courts. Her season stats will probably come down. But a ten-percentage-point increase in first serves in? Nobody does that. Kasatkina won just five games yesterday, and she won’t be the last opponent to discover that whatever edge she once had against Rybakina is gone.

Average ballast

As Ivo Karlovic can tell you, the best service in the world can take you only so far. Some first serves will go astray, some serves will come back, and then there’s the whole return game to contend with. Women’s tennis rarely features characters quite as one-sided as Ivo, but Vekic and Garcia illustrate the point, struggling to string together victories because their serves alone are not enough.

Here’s a quick overview of how the rest of Rybakina’s game stacks up against the average top-50 player over the last 52 weeks:

Stat     Top-50  Elena  
2nd W%    46.7%  48.4%  
DF%        5.2%   3.9%  
RPW       44.4%  44.2%  
Break%    35.5%  36.9%  
BPConv%   46.6%  43.5%

She’s somewhat better than average behind her second serve, as you’d expect from someone with such a dominant first serve. It’s aided by fewer double faults than the norm. On return, we have two separate stories. Taking all return points as a whole, Rybakina is almost exactly average, matching the likes of Barbora Krejcikova and Marta Kostyuk. The only category where she trails the majority of the pack is in break point conversions–and by extension, breaks of serve.

The discrepancy between Rybakina’s results on break points and on return points in general may just be a temporary blip. Most players win more break points than their typical return performance, because break points are more likely to arise against weaker servers. That hasn’t been the case for Elena in the last 52 weeks, and it wasn’t in 2022, either, when she won 41.9% of return points that year but converted only 40.5% of break opportunities.

Match Charting Project data indicates that she is slightly more effective returning in the deuce court than the ad court; since most break points are in the ad court, that could explain a bit of the gap. Charting data also suggests she is a bit more conservative on break point, scoring fewer winners and forced errors than her normal rate, though not fewer than the typical tour player. It may be that Rybakina will always modestly underperform on break opportunities, but it would be unusual for a player to sustain such a large gap.

In any case, she hasn’t struggled in that department in 2024. In 13 matches, she has won 46.9% of return points overall and 47.3% of break points. It’s dangerous to extrapolate too much from a small sample, especially on her preferred surface, but it may be that Rybakina’s single weak point is already back to the top-50 norm of her overall return performance.

The value of all this average is this: What Rybakina takes with her first serve, she doesn’t give back with the rest of her game. We’ve already seen how a standout rate of unreturned first serves–plus a bunch of average-level support from her second serve and ground game–translates into elite overall results on serve. A tour-average return game generates about four breaks per match. Elena has been closer to 3.5, but either way, that’s more than enough when coupled with such a steady performance on the other side of the ball.

I can’t help but think of Rybakina’s “other” skills as analogous to the supporting cast in team sports. Her first serve is an all-star quarterback or big-hitting shortstop; the rest of her game is equivalent to the roster around them. In baseball, a league-average player is worth eight figures a year. Though Elena’s return, for instance, doesn’t cash in to quite the same degree, it is critical in the same way. A superstar baseball player can easily end up on a losing team, just as Caroline Garcia can drop out of the top 50 despite her serve. Rybakina is at no risk of that.

A final striking attribute of Rybakina’s game is that her array of tour-average skills can neutralize such a range of opponents. Her weekend in Abu Dhabi was a perfect illustration, as she overcame Samsonova and Kasatkina, two very different opponents, each of whom has bedeviled her in the past. Elena is more aggressive than the average player, but she is considerably more careful than Samsonova; her Rally Aggression Score is equivalent to Swiatek’s. She was able to take advantage of the Russian’s rough patches without losing her own rhythm or coughing up too many errors of her own.

Against Kasatkina, she posted the most unexpected “average” stat of all. In a matchup of power against defense, defense should improve its odds as the rallies get longer. On Sunday, the two women played 15 points of ten strokes or more, and Rybakina won 8 of them. In her career, Elena has won 52% of those points–probably more by wearing down opponents with down-the-middle howitzers than any kind of clever point construction, but effective regardless of the means.

Rybakina won’t beat you at your own game. But she’ll play it pretty well. Combined with the best first serve in women’s tennis, drawing even on the rest is a near-guarantee of victory. Abu Dhabi marked her seventh tour-level title, and it will be far from her last.

* * *

Ugo Humbert, Elo top-tenner

You probably don’t think of Ugo Humbert as a top-ten player, if you think of him at all. The 25-year-old left-hander cracked the ATP top 20 only a few months ago, and his title last week in Marseille gave him a modest boost to #18.

Elo is much more positive about the Frenchman. Today’s new Elo rankings place him 9th overall, just behind Hubert Hurkacz, the man he defeated to reach the Marseille final. Humbert has always been dangerous against the best, with a 22-25 career record facing the top 20, and a 10-12 mark against the top ten.

Humbert’s place in the Elo top ten might feel like a fluke; there’s a tightly-packed group between Hurkacz at #8 and Holger Rune at #13, and an early loss in Rotterdam could knock the Frenchman back out of the club. But historically, if a player reaches the Elo top ten, a spot in the official ATP top ten is likely in the offing.

I wrote about this relationship back in 2018, after Daniil Medvedev won in Tokyo. As his ATP ranking rose to #22, he leapt to #8 on the Elo list. In retrospect, it’s odd to think that “Daniil Medvedev will one day crack the top ten” was a big call, and it wasn’t that far-fetched: Plenty of people would’ve concurred with Elo on that one. He made it, of course, officially joining the elite the following July.

In that post, I called Elo a “leading indicator,” since most players reach the Elo top ten before the ATP computer renders the same judgment. This makes sense: Elo attempts to measure a player’s level right now, while the ATP formula generates an average of performances over the last 52 weeks. That’s a better estimate of how the player was doing six months ago. Indeed, for those players who cracked both top tens, Elo got there, on average, 32 weeks sooner. In Medvedev’s case, it was 40 weeks.

Most importantly for Humbert, Elo is almost always right. In October 2018, I identified just 19 players who had reached the Elo top ten but not the ATP top ten. Three of those–Medvedev, Stefanos Tsitsipas, and Roberto Bautista Agut–have since taken themselves off the list. One more has come along in the meantime: Sebastian Korda joined the Elo top ten in early 2023, but his ATP points total has yet to merit the same ranking.

Most of the Elo-but-not-ATP top-tenners had very brief stays among the Elo elite: Robby Ginepri qualified for just one week. The only exception is Nick Kyrgios, who spent more than a year in the Elo top ten, thanks to his handful of victories over the best players in the game. His upsets earned him plenty of notoriety, but his inability to consistently beat the rest of the field kept his points total deflated.

Humbert, in his much quieter way, fits the same profile. His serve means that he can keep things close against higher-ranked players, but he has struggled to string together enough routine wins to earn more of those chances. (Injuries haven’t helped.) Still, the odds are in his favor. In 32 weeks–give or take a lot of weeks–he could find himself in the ATP top ten.

* * *

Surfaces in South American Davis Cup

It dawned on me about halfway through the deciding rubber of the Chile-Peru Davis Cup qualifying tie: They were playing on a hard court! In South America! Against another South American side!

It made sense for Chile, with big hitters Nicolas Jarry and Alejandro Tabilo leading the team, and they did indeed vanquish the Peruvian visitors. But South America is known as a land of clay courts, the home of the “Golden Swing.” It seemed weird that an all-South American tie would be played on anything else.

As it turns out, it isn’t that unusual. Since the late 1950s, I found 252 Davis Cup ties between South American sides. I don’t have surface for 37 of them, almost all from the 1970s. Presumably most of those were on clay, but since that’s the question I’m trying to answer, I’m not going to assume either way.

That leaves us with 215 known-surface ties, from 1961 to the Chile-Peru meeting last weekend. (I’m excluding the matchup between Argentina and Chile at the 2019 Davis Cup Finals, since neither side had any say in the surface.) To my surprise, 37 of those ties–about one in six–took place on something other than clay. That’s mostly hard courts, but five of them were played on indoor carpet as well.

The country most likely to bust the stereotype has been Venezuela, which preferred hard courts as early as the 1960s. Ecuador also opted to skip clay with some frequency; it accounted for the first appearance of carpet in an all-South American tie back in 1979.

Chile has generally stuck with clay, but not always. The last time they hosted a South American side on another surface was 2000, when they faced Argentina on an indoor hard court. The surface probably wouldn’t have mattered, as Marcelo Rios and Nicolas Massu were heavy favorites against a much weaker Argentinian side. Though they won, the home crowd was so disruptive that the visitors pulled out without playing the doubles. Chile was disqualified from the next round and barred from hosting again until 2002.

The crowd last weekend was typically rowdy, but Jarry and Tabilo advanced without controversy. For some South American sides, hosting on hard courts may finally become the rule, not the exception.

* * *

Subscribe to the blog to receive each new post by email: