Category: Serve statistics

What Does Felix Auger-Aliassime Do So Right On Indoor Hard Courts?

Felix Auger-Aliassime has earned a reputation as a world-beater on indoor hard courts. He’s no Jannik Sinner–as Sinner reminded him all four times they met last year, twice indoors–but FAA is a fearsome customer against just about anybody else.

Last week the Canadian added to his indoor title haul with his second-straight championship in Montpellier. This time, he straight-setted Adrian Mannarino. While that win doesn’t particularly raise any eyebrows, the body of work keeps growing. It’s his eighth career title indoors, three of them at ATP 500s. Last fall in Paris, he also reached his second Masters final. (The first was in Madrid, the indoorsiest of the clay Masters.)

What’s the secret?

The conventional wisdom is that he has a big game, especially a deadly first serve. The controlled environment indoors, plus typically fast conditions, play to his strengths. The serves skid across the court even faster. His weaknesses are mitigated because the bounce is more predictable and because points are shorter.

All that sounds plausible. My only gripe is, couldn’t you say that about a lot of players? The whole paragraph applies, almost word for word, to Hubert Hurkacz, who has two Masters crowns on outdoor hard, plus a clay title, yet just a pair of indoor 250-level championships. What about Matteo Berrettini? The description might match him even better, yet the Italian has never won a title indoors. He has reached only one indoor 250-level final.

Before we go to the numbers, let me give you my seat-of-the-pants theory. FAA has huge weapons, but he doesn’t always play like it. He doesn’t consistently swat away easy plus-ones like Berrettini does. He gets sucked into long rallies, where he’s often at the disadvantage. Indoors, though, he knows what the tactics are, and he plays the way he should play. Indoor Felix, then, is the best Felix, both because his game is suited to the conditions and because he shows up with the right approach.

On the other hand, the last two points against Mannarino on Sunday were 8- and 18-shot rallies, respectively. So, you know, don’t trust my pants.

Numbers!

You can, however, trust the spreadsheets. The Match Charting Project has well over 100 Auger-Aliassime matches. Going back to 2020, the total includes 41 on indoor hard and 40 on outdoor hard, nicely suited for some comparisons. I was tempted to throw out the seven Tour Finals matches from the indoor tallies, because they skew the quality of the opponents, but the Canadian’s indoor averages are about the same with or without them.

Start with serve stats:

Surface       Unret%  <=3 W%  RiP W%  
Indoor Hard    35.7%   47.7%   55.5%  
Outdoor Hard   32.8%   43.4%   49.7%

About three percentage points more serves don't come back, and there's an even wider gap in points polished off on the serve or plus-one (the "<=3 W%" stat). The biggest gap here is in points won when the return comes back. Sub-50% is below average, especially for hard courts. 55% or better is very good, even in fast conditions.

Almost all of the indoor/outdoor serve differences are thanks to the first serve. FAA's second-serve numbers are about the same regardless of roof status.

Of course, Felix isn't the only guy on tour who wins more easy serve points indoors. I don't have comprehensive stats on the indoor/outdoor split, so I can't tell you the exact tour average. But we can compare how much Auger-Aliassime gains on serve to how much he gives up on return:

Surface        RiP%  RiP W%  
Indoor Hard   65.3%   48.8%  
Outdoor Hard  67.5%   43.2%

He retrieves 2.2 percentage points fewer serves indoors--better than the 2.9-percentage-point difference he gains on serve. But when he gets the serve back, he's actually better indoors than outdoors! He gains five percentage points in that department on serve, and he gains the same margin on return.

This might dovetail with the conventional wisdom. His monster serve really pays off indoors. And predictable conditions give him a bit of cover on return.

Whatever the reason, Auger-Aliassime's groundstrokes are way more effective indoors. My Potency metrics, FHP and BHP, combine winners, unforced errors, and shots that set up winners and errors. They give you one-number estimates of how valuable each shot is, and... wow:

Surface       RallyLen  FHP/100  BHP/100  
Indoor Hard        3.7     +8.5     +0.0  
Outdoor Hard       3.9     +3.2     -5.8

His indoor points are a little shorter, but I assume that is typical. I would've guessed that the difference was greater.

The Potency numbers (expressed here as rates per 100 shots), tell a more emphatic story. A +3.2 FHP/100 is ok, not great. Tommy Paul and Ugo Humbert are in that zone. On the other hand, +8.5 is the 52-week average of Carlos Alcaraz. A -5.8 BHP/100 is near the bottom of the pack, below the likes of Ben Shelton and Grigor Dimitrov. By contrast, +0.0 is, as it sounds, a good solid average.

These numbers don't drill into the "why" questions that naturally follow. But they help us pick between theories. I suspect that much of the difference in groundstroke stats has to do with the shots he gets to hit. The winners are downstream of good serves. Auger-Aliassime picks up some aces, but he picks up more plus-one (or even plus-two) winners, and those make his forehand and backhand numbers look good.

The "indoor predictability" thesis also looks good here. Remember that everybody should benefit from that--and not everybody's numbers improve like Felix's do--but it may be that the Canadian is more-than-typically exposed by the vagaries of outdoor play.

All the angles

Quick thought experiment. Picture Roger Federer hitting an ace.

Now imagine Auger-Aliassime hitting an ace.

What specific serves came to mind? If you're like me, you pictured Federer shooting a bullet right down the tee. And then you visualized FAA hitting a flat bomb out wide.

Of course, both guys hit plenty of aces in every direction. The charting stats suggest that Felix has a slightly better chance of an ace when he goes up the middle. (Federer did too, by a bigger margin, as do most players.) Still, this indoor/outdoor split caught my eye:

Surface       Deuce Wide%  Ad Wide%  BP Wide%  
Indoor Hard         50.5%     47.8%     33.7%  
Outdoor Hard        46.9%     45.2%     41.0%

Each column shows how often Auger-Aliassime opted for a wide serve in various scenarios. The first-serve differences are probably more marked, because his second-serve tendencies are about the same.

Indoor, he goes wide more often--but less often under the pressure of break point. While the margins are rather slim, it seems like the wide serve becomes his bread-and-butter indoors, and he uses the tee serve to mix things up on break point--because he's hitting more wide serves the rest of the time.

Wide serves are more likely to come back, but they don't make the returner any more likely to win the point. Especially against Felix: His signature serve might not even be an ace, but a wide bomb that the returner just barely plops back over the net.

The fact that he hits more wide serves indoors explains a lot. He gets a few more unreturned serves (as everybody does, probably), but he gains more of an advantage on the serves that (weakly, oh so weakly) come back. His groundstroke stats sparkle, padded by those easy balls.

Here's one final comparison:

Surface       2ndAgg  
Indoor Hard       +7  
Outdoor Hard     +46

"2ndAgg" is the Aggression Score stat tailored specifically to second serves. A higher score means more double faults and more unreturned second serves. Lower means fewer risks on second balls. +7 is quite conservative: Only about a dozen players consistently score so low.

But--those careful second servers include Sinner, Hurkacz, and Berrettini. With a game like Auger-Aliassime's, the second serve isn't the time to take risks. And indeed, in all of his indoor finals, he has never topped a double-fault rate of 5%. In the Montpellier final, he missed his second serve just once, and he committed no double faults at all in the quarter- and semi-finals.

Here, finally, is some support of my seat-of-the-pants theory, that when Felix goes indoors, he plays the way he ought to be playing all the time. He stays within himself, which is still imposing enough to earn a lot of cheap points. It's not a particularly complicated story, and I'm still not convinced why it doesn't apply to a half-dozen other guys on tour. Maybe it is all about the wide serve, the signature shot that allows Auger-Aliassime to manage risk and put his opponents on the back foot, all at the same time.

Carlos Alcaraz Will Return Your Serve. Good Luck With That.

It often feels fruitless to pick out the strongest aspects of the Carlos Alcaraz game. (Sinner’s, too, of course.) He is so good at everything that we tend to focus on the same few particularly attention-grabbing attributes. The knee-buckling dropshot, the outrageous will to win (and corresponding fifth-set record), the forehands at full stretch.

We don’t ask often enough why Alcaraz or Sinner won a match, because it seems obvious. They’re simply better than everybody else, except for maybe Novak Djokovic or Cameron Norrie on a good day.

And it’s true, there’s no single reason why. (There’s never a single reason for anybody, though most players make it easier to isolate a small number of effective shots or tactics.) All we can do is focus on one part of the Alcaraz game, then goggle at it.

Today, let’s goggle at the return of serve.

Here’s a fun place to start. Djokovic completed five matches at the Australian Open. Take a look at his first-serve win percentages from those five matches:

Opponent           1st W%  
Martinez            93.2%  
Maestrelli          86.0%  
van de Zandschulp   77.0%  
Sinner              71.4%  
Alcaraz             65.9%

Djokovic, at any age, is an outstanding hard-court server. 71.4% is below average: Sinner did a nice job on return, even if he forgot on some break points. 65.9%, though, is unreal. Of the ATP top 50, how many players do you think win fewer than 66% of their first-serve points? One: Sebastian Baez. Alcaraz turned Djokovic into Sebastian Baez.

It wasn’t a fluke, either. Djokovic won 66.1% of first-serve points against Alcaraz in the US Open semi-final last year. Those two aren’t the absolute worst serving performances of Djokovic’s last twelve months–Vacherot held him to 60.5% in Shanghai, and Musetti kept him to 61% in their abbreviated match–but they are close.

Two separate skills

Charting data allows us to break down service returns into two components:

  1. Getting serves back
  2. Winning points after getting the serve back

Pretty straightforward stuff. You want to get as many serves back as possible, but you also want to set yourself up to win points after you do.

There’s something of a tradeoff here. Jaume Munar is a good example of somebody who retrieves a ton of serves but loses a lot of the points because he doesn’t do enough with the return. Andrey Rublev is the opposite, not getting many returns back, but winning a relatively high percentage when he does. Adjusting for surfaces and opponent quality, the end result for Munar and Rublev is about the same, even if they get there via such different routes.

The tradeoffs don’t apply to everyone. Take a look at the scatterplot, which shows percentage of returns in play, and in-play return-points won, for all ATPers with at least ten charted matches in the last 52 weeks. The higher you are above the green regression line, the better. You can mouse over each dot for player details, but I don’t need to tell you whose dots are red:

ATP Returns in Play

10+ charted matches (last 52 weeks) • RiP% vs RiP Win%

Sinner & Alcaraz
Mere Mortals
Regression Line

Both halves of Sincaraz get more returns back than average, and they win more of those in-play points than anybody else.

(How they win the in-play points is itself a multifaceted question. Both Sinner and Alcaraz rank in the top six by my forehand and backhand potency metrics, and Alcaraz’s backhand rating continues to creep upwards. I also dug into their shot tolerance last year and found new statistical categories for them to lead.)

Remember I started out by talking about first-serve returns. That’s where Alcaraz really shines, even above his brother in world domination. Same idea, first-serve returns only:

ATP First-Serve Returns in Play

10+ charted matches (last 52 weeks) • 1st Serve RiP% vs RiP Win%

Sinner & Alcaraz
Mere Mortals
Regression Line

Alcaraz is the right-most red dot. There are 36 players on that plot, and Alcaraz gets more first serves back than all but four of them. (And he’s basically tied with Medvedev, the blue dot underneath his.) There’s no tradeoff for Carlitos: He gets more balls back than almost anybody, and he wins more of those points than anybody except for Arthur Fils (barely), Sinner (barely), and Rublev (whack!).

Both skills were on display in Sunday’s final. Alcaraz put an astonishing 76.5% of Djokovic’s first serves in play–almost off the right side of the scatterplot, against an elite opponent, on a hard court. I say “astonishing,” but was it even a surprise? At the US Open, Alcaraz got 75% of Novak’s first serves back.

When you can handle so many first serves, the win rate barely matters, but of course Carlitos did fine in that department as well, winning 44.6% of those in-play returns in Melbourne. Lower than his usual rate by a healthy margin, but hey, it was still Djokovic, and a massive number of in-play returns is always going to include a fair few weak ones.

When I started looking at returns in play about a decade ago, the tradeoff was clearer. More players fit the Munar or Rublev molds, getting a lot of serves back, or winning a high percentage of points when they did–but not both. Now, the relationship between the two stats is positive, but only slightly. They’re best understood as unrelated.

But for Alcaraz, tennis is built out of a dozen or so unrelated skills–all of which allow him to tower over the field. Sinner is close enough, and his serve might tilt the scale slightly in the other direction. Everybody else, though, is left scratching their collective head. Djokovic became the greatest of his generation by taking away opponents’ second serves. When Alcaraz neutralizes your first, what’s left?

The Rybakina Serves That Tipped the Scale In the Melbourne Final

In Saturday’s Australian Open final, Elena Rybakina won 92 points. Aryna Sabalenka won 92 points. Rybakina won 76% of her first serve points; Sabalenka won 75%. Both players held on to 48% of their seconds. Even their average first serve speeds were nearly identical, Rybakina’s 178 km/h nipping Sabalenka’s 177 km/h.

Only a few moments really mattered. Sabalenka converted two of eight break points. Rybakina converted three of six.

With such narrow margins, we should be cautious to draw conclusions about tactics and player skills. Flip one or two of those break opportunities, and it would have been a very different trophy ceremony. Anybody who tries to tell you “why” Rybakina won should keep that in mind. Still, Sabalenka would surely like to know how to secure another half-dozen points and put the result out of the range of luck. Rybakina will hope to do the same.

Pick target, hit target

Rybakina is the best server in the women’s game. Her ace rate over the last year is better than 10%–a percentage point ahead of second place (Osaka), and miles ahead of Sabalenka’s 6%. Rybakina has won nearly 75% of her first-serve points, while no one else cracks 73% and only a few players are on the north side of 70%.

At key moments on Saturday, Rybakina dazzled with her ad-court serves out wide. She saved the only two break points she faced in the first set with back-to-back unreturned serves, both wide. She finished the match with another signature delivery, acing Sabalenka out wide on match point.

If you’re looking for a “why,” it’s tempting to focus on those wide ad-court serves. Rybakina made 18 first serves when she aimed for that corner, and she won 14 of those points.

But! It’s not the ad-wide corner, specifically. Rybakina was even deadlier when she targeted Sabalenka’s backhand corner in the deuce court. She landed 14 of those first serves, winning 13.

Here’s the Rybakina method for defeating the world number one:

  1. Have a world-class serve
  2. Aim first serves at the backhand corner
  3. Make half of them

Easy, right?

Apparently not easy

Fair enough, most players don’t have anything like Rybakina’s serve. A few–Osaka, Noskova, Qinwen–can do a decent impression on a good day. Still, it’s an uphill battle to knock off Sabalenka with aggression from the line.

What’s striking, though, is that most opponents don’t really try.

Across 120+ charted matches since the beginning of 2024, Sabalenka’s opponents aimed their first serve at her backhand corner about 40% of the time. (That doesn’t mean they aimed 60% at the forehand corner: A fair number of first serves don’t land close to either corner.) In the vast majority of matches, her opponent aimed half or fewer of their first serves at her backhand corner.

On Saturday, Rybakina targeted the backhand corner 63% of the time.

The first serves that landed in were so devastating in part because she took a low-margin approach. Rybakina already misses more first serves than almost anyone on tour: Her 57.4% first-serve-in rate is worse than 45 of the top 50 women. Against Sabalenka, she succeeded exactly half the time when she fired in that direction. Corner-aimed serves are (unsurprisingly) lower-percentage for everybody, but her 50% was even worse than tour average.

It’s a smart tradeoff. Combine the two numbers, and we see that on 32% of her service points, Rybakina put a first serve in play to Sabalenka’s backhand corner. Those, as we’ve seen, are as close to guaranteed points won as you can find. Sure, that leaves 68% of service points to worry about. Yet as much as Rybakina’s premier weapon glitters, she’s a solid average at everything else. She’ll pick up a lot of those other points with quality second serves or rocket-powered firsts to the forehand corner, or by winning baseline rallies.

In the past two years, only a handful of players have managed to put first serves to Sabalenka’s backhand corner on as many as 32% of points. Even then, it doesn’t always work: Marketa Vondrousova, for instance, is unparalleled at hitting her targets, but her deliveries are softballs in comparison. For the players who can serve big, though, Rybakina may have pointed the way to tougher challenges against the world number one.

Ka-zam

This might be a recent refinement to Rybakina’s match tactics. We have over 80 charted matches for her since the beginning of 2024, and she has rarely aimed so many of her serves at the backhand corner. To be clear, she doesn’t need to. She straight-setted Sabalenka for the year-end title in November with only 44% of first serves pointed at that target.

But suggestively, Rybakina hit nearly as many first serves to the backhand corner in her Australian Open quarter-final match against Iga Swiatek. While she wasn’t quite as successful, landing just 40% of those attempts, the end result was encouraging. Even with all the misses, backhand-corner firsts accounted for a quarter of her service points. And she was as eye-poppingly successful on those points against Iga as she was in the final. Swiatek salvaged just 1 of 12.

It remains to be seen whether this is repeatable. When Rybakina is serving at her best, peppering the backhand corner is probably a good way to take advantage. (Unsurprisingly, since this is something tennis coaches tell twelve-year-olds.) If she’s misfiring, low-percentage first serves are probably not the way to fight her way through.

And surely, the world number one will start taking a few more backhand-return reps. She doesn’t have to turn into Andre Agassi to negate Rybakina’s new-found advantage. She just needs to defend that corner a little better. 94 or 95 points would have gotten the job done on Saturday. Even against a world-class serve and superb tactical execution, Sabalenka won 92. The two women will continue jostling for an edge, and it looks like the battle will increasingly take place with Sabalenka leaning to her left.

Aryna Sabalenka, Queen of Clay?

Aryna Sabalenka typically has things more under control, even on clay.

For a while there, it seemed that Aryna Sabalenka and Iga Swiatek would divide the spoils. Sabalenka would dominate on hard courts, and Iga would continue her reign on clay.

At the moment, Aryna is taking it all. She has held the number one ranking for six months now, opening up an astonishing 4,300-point gap on the field. She picked up her third Madrid title on Saturday, straight-setting Coco Gauff shortly after Gauff dealt Swiatek one of her worst-ever clay-court losses. My Elo ratings not only put Sabalenka atop the field, they rank her first on clay. By Elo, at least, the Belarusian will be the favorite at Roland Garros.

Some of this can be explained by Swiatek’s struggles. But Sabalenka has long been ready to seize her chance. Here are her career tour-level results by surface:

Surface     W-L  Win%  Hld%  Brk%  TPW%  
Hard     244-79   73%   75%   37%   53%  
Clay      74-29   72%   74%   38%   53%

This is not the snapshot of a player with a strong surface preference. She has reached ten career clay-court finals, winning three and losing four to Iga.

On the other hand, all three tournament victories (and more final) came in Madrid. Four more of the finals were in Stuttgart. Both events have historically favored bigger hitters: Madrid with its altitude, and Stuttgart with its predictable indoor conditions. Rome and Roland Garros present different challenges.

So, is Sabalenka the new queen of clay, or is her domain limited to the Spanish capital? Is she really the woman to beat in Paris?

Surface sensitivity

Here’s a further breakdown by clay-court event:

Event           W-L   1st%   2nd%    RPW    DR  
Roland Garros  16-7  67.4%  44.5%  47.7%  1.15  
Rome            9-6  65.4%  44.2%  44.3%  1.04  
Madrid         23-4  69.9%  50.6%  44.9%  1.19  
Stuttgart      13-5  69.9%  47.5%  43.2%  1.12

(DR = Dominance Ratio, percentage of return points won divided by serve points lost.)

Madrid stands out as Sabalenka’s playground, and Rome is clearly not her favorite tour stop. But her cumulative stats at the French Open, where she has reached only one semi-final and one other quarter, fit better with the tournaments where she has reached so many finals.

You probably remember Aryna’s tough 6-7, 6-4, 6-4 loss to Mirra Andreeva in last year’s final eight. I had forgotten that it was her fifth straight three-set exit in Paris. Two years ago, it took Karolina Muchova more than three hours to advance to the final. Back in 2020, Sabalenka won more points than Ons Jabeur did in their third-round meeting, yet it was the Tunisian who moved on.

The parade of narrow losses isn’t a case for the Queen-of-Clay title–after all, Iga would’ve won some of those matches in about 56 minutes. It’s merely a reminder that the world number one has often been close. She is playing somewhere near her best-ever tennis right now, so if the improved form carries over to Roland Garros, it’s easy to imagine those close matches finally tipping her way.

Surface insensitivity

Here are some (men’s) surface-speed ratings from the last 52 weeks. Stuttgart is a women’s only event, so I’ve included Hamburg as a rough approximation:

Year  Event          Surface Speed  
2024  Roland Garros           0.66  
2024  Rome                    0.67  
2024  Madrid                  0.82  
2024  Hamburg                 0.89

(I use men’s data for surface speed because the metric is based on ace rate. Men hit more aces, so there’s better data to assess court conditions.)

Tour average, across all surfaces, is 1.0. Speed ratings in the 0.8 to 0.9 range are slow-ish, but they’re more like a slow hard court. For instance, the men’s Masters event in Montreal last year rated a 0.8, almost identical to Madrid. Point being, there is a clear separation between the traditional clay events and the upstarts. It would stand to reason that a big hitter like Sabalenka would struggle more in Rome and Paris.

Despite the trophy count, surface effects don’t show up where I would expect to find them in the stats. The Match Charting Project–thanks to one unhealthily obsessed contributor–has logged almost all of Aryna’s tour-level matches. Based on that data, here are her average rally lengths by event:

Event          Avg Rally  
Roland Garros       3.54  
Rome                3.25  
Madrid              3.30  
Stuttgart           3.14

Sabalenka has defied the slow dirt at the Foro Italico. She has somehow played even shorter points there than in Madrid. We can give some credit to her opponents–she has faced Jelena Ostapenko, Dayana Yastremska, and Danielle Collins there–but even her 2022 match with Iga registered just 3.1 strokes per point.

The same trends–or lack thereof–show up in her serve stats. The next table shows the rate at which Sabalenka’s serves are unreturned, and the percentage of points that she wins with either her serve or her second shot:

Event          Unret%  <=3 W%  
Roland Garros   27.2%   46.9%  
Rome            31.6%   49.0%  
Madrid          30.4%   49.6%  
Stuttgart       36.0%   54.0%

Though Stuttgart is a server's paradise, the gap between Madrid and Rome remains slim. Looking at these numbers, you'd never know that Sabalenka had three titles at one of the events and a 9-6 career record at the other. At the very least, it seems that the slow clay has not prevented the Belarusian from playing her game.

The dropshots

Last year, Sabalenka clay-court game changed. She hit more drop shots than ever, especially in Rome and Paris. My deep dive showed that the tactic was a success across multiple dimensions:

Clay-Sabalenka got the best of both worlds. She won more points by playing the drop, and she won more points because of the tactic’s lingering effect. Perhaps because of her growing reputation as a drop shot queen, the effect has persisted since June, even when she doesn’t go to the well so often.

In theory, dropshots give opponents something to think about, and the positive effect of a good dropshot goes beyond a single point. It's hard enough to handle Sabalenka-level power. Thinking you might have to dash forward makes it even worse. The post-dropshot effect doesn't work for everybody--it is neutral for Ons Jabeur, for example--but it has made Aryna even deadlier.

Expect droppers galore in Rome. Sabalenka unleashed eleven in the Madrid semi-final against Elina Svitolina and another eleven on Coco Gauff in the final. She won 14 of the 22 points. If it works in Madrid, it will almost definitely continue to score points on the more stately surfaces in Rome and Paris.

Sabalenka's new weapon remains a minor tweak, but it has clearly been a positive one. Few women gain so much from dropshotting as she did on slow clay last season.

Coronation?

All of this adds up to Sabalenka being the Roland Garros favorite--mathematically if not emotionally. If she is the new Queen of Clay, it's only by default. Swiatek is a generational talent on the surface: If Iga can play her best, Aryna will be lucky to push the final to three sets.

The case for the world number one, then, is more prosaic. Who could beat her? A resurgent Iga, of course. Andreeva could cause problems again: Perhaps no one else on tour can better neutralize the Sabalenka serve. Ostapenko could blitz her way through, as she did in Stuttgart, but she is even more of a threat to Swiatek than she is to Sabalenka. The luck of the draw is a very real factor when the Latvian is lurking.

The next two weeks in Rome won't overturn any of this, but they could refine the narrative. If Iga coasts to a fourth Italian Open crown, it will be tough to bet against her in Paris. If Aryna comes out on top, she would head to the French as more than just a mathematical favorite. If Ostapenko wins it, well, that would be pretty funny.

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Francisco Cerundolo’s Solid Second Serves

Francisco Cerundolo at Wimbledon in 2022. Credit: Jmmuguerza

I remain mildly obsessed with Francisco Cerundolo’s second-serve stats. It started when I was writing about Jakub Mensik last month. Mensik is one of the worst players on tour at winning points when opponents return his second serve. Cerundolo is the best.

This graph compares points won when first and second serves come back. It is now five weeks old, but the numbers haven’t changed much:

Unfortunately for Cerundolo, this is not a particularly valuable skill. There’s a surprisingly weak correlation between win percentage on returns in play (for first or second serves) and win percentage overall. Men who hit a lot of unreturned serves often end up with mediocre return-in-play win rates, because they don’t have easy plus-one opportunities–those great serves don’t come back at all.

Cerundolo’s second serve almost always comes back. Only 14% have gone unreturned in the last 52 weeks. Of players with at least ten charted matches in that time, only Marcos Giron is lower. Average is 18%, and even Sebastian Baez is at 16%. The Argentinian’s second serve isn’t bad, it’s just not quite as much of a weapon, and his focus is to set up the rally in his favor.

It isn’t just about the return-in-play win rate, though. Cerundolo can rely on his second serve more than most of his peers–sometimes more than on his own first serve.

Trending up

Over the last year, Cerundolo’s second-serve winning percentage is 53.1%, good for 19th among the top 50. (That doesn’t count stats from the ongoing Madrid tournament.) Nothing special, though still a respectable number for a guy whose serve is not his foremost weapon.

In 2025–still not counting Madrid–he’s up to 54.1% and 14th place, a couple ticks behind Jack Draper. Tack on his four wins so far at the Caja Magica, and he’s up to 55.5%.

Like many guys with games tailored for clay, the gap between Cerundolo’s first and second serve stats is smaller than average. Going back to the last 52 weeks, here are the top ten smallest ratios between first- and second-serve win percentages, along with tour average and the man at the other extreme, Mensik:

Player               1st%    2nd%  2nd/1st  
Sebastian Baez       63.6%  50.4%    0.792  
Carlos Alcaraz       73.4%  56.7%    0.772  
Davidovich Fokina    67.2%  51.9%    0.772  
Lorenzo Musetti      69.7%  53.2%    0.763  
Tommy Paul           71.9%  54.8%    0.762  
Francisco Cerundolo  69.7%  53.1%    0.762  
Tomas Machac         69.8%  53.0%    0.759  
Casper Ruud          71.4%  53.8%    0.754  
Holger Rune          73.0%  54.9%    0.752  
Alex de Minaur       73.4%  54.5%    0.743  
…                                           
Top 50 Average       73.6%  52.4%    0.712  
…                                           
Jakub Mensik         76.5%  46.6%    0.609

By the end of that list, you’ll have to knock the clay off your soles. This is another metric in which Cerundolo is reaching new heights this season. So far in 2025 (including Madrid), he’s won 70% of firsts and 55.5% of seconds, for a ratio of 0.793, just edging out Baez.

These narrow gaps aren’t really about good second serves. They reflect game styles built around modest first serves and strong baseline play. Most serves come back, and when they do, it doesn’t matter much which serve kicked things off.

It’s also just what happens on slower courts. The average top-50 player sees his first-serve win rate drop to 70% on clay, resulting in a ratio of 0.744–just about even with Alex de Minaur.

High seconds

The quirks that got me hooked at Cerundolo’s second-serve stats are the occasions when he wins more second-serve points than first-serve points. He did it against Tommy Paul at Indian Wells, in his semi-final loss to Ben Shelton in Munich, and again to kick off his Madrid campaign against Harold Mayot.

This is another clay-court kind of thing. Since the beginning of last season, only two men have accomplished the feat more often than the Argentinian has:

Player               Matches   2>1s  
Sebastian Baez            76     12  
Casper Ruud               91     12  
Francisco Cerundolo       87      9  
Mariano Navone            61      8  
Davidovich Fokina         67      8  
Lorenzo Musetti           81      8  
Alex Michelsen            81      8  
Alex de Minaur            92      8

Once again, the stat has as much to do with pedestrian first serving as it does with strong second-serve execution. Since the start of 2024, the player who has won 60% of his second-serve points most often is Jannik Sinner. Despite clearing that line 44 times, his second-serve win rate has never been higher than his first-serve mark.

When Cerundolo is at his best, no serve–first or second, his or his opponent’s–matters much. Here are his win percentages by rally length over the last 52 weeks:

Length   Win%  
1 to 3  47.6%  
4 to 6  50.1%  
7 to 9  50.7%  
10+     57.3%

The short-point stat tells us that Cerundolo doesn’t win as many quick serve points as his opponents do. Then, the longer the rally drags out, the more things tilt in his favor. Most players struggled to keep their ten-plus number much above 50%. 57.3% is outstanding, highest among any player with at least ten charted matches.

Second thoughts

None of these numbers identify any unique superpower. Cerundolo is a throwback clay-court specialist, much like his coach, Pablo Cuevas. He serves because he has to, then he launches inside-out forehands until his opponents finally surrender.

The skills I’ve isolated do a great job explaining yesterday’s defeat of Mensik in the Madrid quarterfinals. The match was close, with the Argentinian winning 94 points to Mensik’s 91. The Czech was two points from victory in the second-set tiebreak.

Yet despite occasional bursts of return aggression from Mensik, Cerundolo’s second serve never faltered. He won 21 of his 33 second-serve points, including 75% in the pivotal second set. His opponent hit 33 second serves as well, and despite averaging the same speed on those deliveries–96 miles per hour–Mensik won only 14.

That’s more than enough to explain the end result. Long-rally prowess will do the job, too. Mensik entered the match with a 11-4 tiebreak record on the season. When I wrote last month about the Czech’s performance in breakers, I pointed to his ability to keep points short, something that most players are unable to do under end-of-set pressure. Well, in yesterday’s second-set tiebreak, Cerundolo got enough balls back to push the average rally length to 5.6 strokes. He took Mensik’s biggest weapon off the table.

In today’s semi-final against Casper Ruud, Cerundolo faces a different challenge entirely. As we’ve seen, the Norwegian is another player for whom the serve is little more than a formality. Last time they met, in Miami, it was Ruud who won more second-serve points than firsts. Today’s meeting may give us more quirky stats, but the serves themselves are unlikely to tell much of the story.

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Jakub Mensik, Giant Killer

Watch out

On Saturday, Jakub Mensik did it again. Jack Draper was coming off an Indian Wells title, the fortnight of his career, but Mensik was a little bit better. Both sets went to tiebreaks, and twice, at six-all, the 19-year-old Czech took his serving to a new level. He won 14 of 19 tiebreak points and sent the Brit home early.

After such an assured performance, Mensik’s third-rounder felt like a gimme. Roman Safiullin gave him two looks at break points, and that’s all he needed. Behind another monster serve barrage, the Czech waltzed into the fourth round, 6-4, 6-4.

Mensik currently stands outside the top 50, but his ranking doesn’t tell the full story. For one thing, he made his top-50 debut late last year, and his Miami points will almost certainly be enough for him to return. Beyond that, he has proven that he fears no one on tour. Draper was his 6th top-ten win in 11 tries. What’s more, Mensik won a set in three of the five losses, including a meeting in Shanghai last fall with Novak Djokovic.

Djokovic called him “one of the best servers we have in the game.” Indeed, since the US Open last year, the six-foot, four-inch Mensik is cracking aces on more than 15% of his serve points. Only Giovanni Mpetshi Perricard and Quentin Halys rate better among tour players. He has taken things to a new level in Miami. In each of his three matches–against Roberto Bautista Agut, Draper, and Safiullin–he has hit an ace on at least 26% of his serve points. That’s Reilly Opelka-level serve dominance, and even Opelka hasn’t posted three straight ace rates like that since 2022.

Mensik is one of the most exciting prospects on tour, yet Joao Fonseca-mania doesn’t leave much attention to anyone else. What do we make of those top-ten wins… and the non-top-ten losses that have kept him on the edge of the top 50? How should we rate the rest his game–you know, those occasions when he doesn’t end the point with a first serve? Let’s dig in.

Proof of concept

Here is the top-ten record:

Pretty good for someone with another five months left in their teens.

Draper wasn’t the first top-tenner that Mensik overpowered. In the six wins, the Czech held serve 90% of the time, winning three-quarters of first serve points. Djokovic and Alex de Minaur figured out how to neutralize the serve, but lesser returners (read: most other humans) have not.

Even before the Miami upset, Mensik was just the 21st player since the beginning of the ATP rankings to win at least five of his first ten meetings with top-tenners. (I’m excluding players who were already established in 1973, when the points table debuted.) He’s just the 12th ever to win six of eleven. Here’s the full list:

Player               First 10  First 11  
Alberto Mancini           7-3       7-4  
Miloslav Mecir            7-3       7-4  
Fernando Gonzalez         6-4       7-4  
Marc Kevin Goellner       6-4       7-4
Lleyton Hewitt            6-4       6-5  
Jakub Mensik              5-5       6-5  
Ugo Humbert               5-5       6-5  
Marcos Baghdatis          5-5       6-5  
Marat Safin               5-5       6-5    
Carlos Moya               5-5       6-5  
Chris Woodruff            5-5       6-5  
Magnus Larsson            5-5       6-5  
Boris Becker              5-5       6-5  
Fabian Marozsan           5-5       5-6  
Aslan Karatsev            5-5       5-6  
Matteo Berrettini         5-5       5-6  
Reilly Opelka             5-5       5-6  
Mardy Fish                5-5       5-6  
Nicolas Kiefer            5-5       5-6  
Henrik Holm               5-5       5-6  
Greg Holmes               5-5       5-6

It’s a strong list, if a bit scattershot. We have all-time greats, plus Aslan Karatsev and Greg Holmes, who apparently upset both Mats Wilander and Jimmy Connors. The playing styles might tilt a bit toward heavy hitting and big serving, but not overwhelmingly so.

I mention playing styles because rocket serves, like Mensik’s, have a way of turning matches into coin flips. If the serves aren’t coming back, it doesn’t matter how well the guy returns. Other skills fall by the wayside: We’re headed for a tiebreak. Apart from a pair of early breaks, that’s what happened in the Draper match. John Isner won three of his first ten top-ten encounters, and Opelka earned a spot on this list.

Everything else

When the serves do come back, though, it’s anybody’s ballgame, top-ten opponent or not. For Mensik, just about everything apart from the first serve is a relative weakness. In the last 52 weeks, he has won just 47.4% of his second-serve points, worse than 49 of the top 50 players. (Pedro Martinez is the one guy with a sub-Mensik number.)

The Czech has gotten accolades for his backhand, but it’s not really a weapon. While it doesn’t hold him back, it rates about tour average by my Backhand Potency (BHP) metric. His Forehand Potency is the real issue. At just +1.1 per 100 forehands, he ranks ahead of only a few of his colleagues, including Opelka, Mpetshi Perricard, and Hubert Hurkacz. Hurakcz has proven that it’s possible to hang around the top of the game without much help from the forehand, but it’s a narrow path to follow.

All this adds up to some painful numbers in rallies. I was going to say “long rallies,” but Mensik starts to see a disadvantage about as soon as the word “rally” comes into play. In eleven charted matches over the last 52 weeks (not counting the Draper upset), here are how his results shake out by rally length:

Length      Win%  
1-3 shots  52.2%  
4-6 shots  45.3%  
7-9 shots  41.9%  
10+ shots  42.0%

52% on short points is great! That was enough to crack the top ten list when I looked at the same category last week in the context of Draper’s excellence. Since these stats encompass both serve and return, it tells us that he’s cleaning up more of his own quick points than his opponents can manage of their own.

The rest of the story, though, is bleak. He ranks near the bottom in all three of the other categories. If we lump them together, he win the fewest points of anyone with at least ten charted matches in the last year:

Player              1-3 W%  4+ W%  
Jakub Mensik         52.2%  43.8%  
Mpetshi Perricard    51.6%  43.8%  
Zhizhen Zhang        48.5%  44.1%  
Jiri Lehecka         51.8%  44.2%  
Ben Shelton          50.5%  44.7%  
Hubert Hurkacz       55.0%  45.4%  
Lorenzo Sonego       52.5%  45.5%  
Tallon Griekspoor    49.8%  46.1%  
Flavio Cobolli       44.9%  46.6%  
Alexei Popyrin       50.4%  46.8%  
…                                  
Jack Draper          53.3%  48.8%  
…                                  
Stefanos Tsitsipas   50.5%  50.6%  
…                                  
Alexander Zverev     53.0%  53.1%  
…                                  
Novak Djokovic       53.7%  54.9%  
Carlos Alcaraz       52.5%  55.8%  
Jannik Sinner        54.4%  57.0%

Somehow, it gets even worse. With enough short points, weak long-rally skills are survivable. Yet Mensik plays more long points than most of these guys in the bottom ten. The 1-to-3-shot category accounts for less than 63% of his points, while it makes up more than 70% of Mpetshi Perricard’s. Even Jiri Lehecka, hardly an extreme case like GMP, comes in at 66%.

Second to last

Mensik is hardly an elite returner, but he is good enough for now. He has won about 37% of his return points over the last 52 weeks, a rate that–coupled with strong serving–is sufficient to get him into the top ten. Despite his relatively low ranking, he has posted those numbers against high-quality competition. His median opponent has been stronger than those faced by Stefanos Tsitsipas or Casper Ruud.

The immediate concern for the Czech is his second serve. I mentioned earlier that he wins barely 47% of those points. Ben Shelton, who wins exactly as many first-serve points as Mensik does, converts 55% of his seconds. While that’s unusually good, nearly every player in the same first-serve territory wins at least 51% behind the second serve.

This is a good time to remember that Mensik is 19. He hasn’t been six-foot-four for long. It’s possible that his second serve will look entirely different in two years than it does today. He’ll certainly hope so. He misses more than 12% of his seconds, a double-fault rate that would be acceptable only if he were taking chances and reaping the rewards of those risks. At the moment, he’s just struggling.

The second-serve weakness is more than enough to flip the outcome of a match. In the last year, when Mensik has landed at least 60% of his first serves, his record is 16-5. Under 60%, it’s 12-17.

The root of the problem is what happens when the second serve comes back. The Czech’s second delivery isn’t yet strong enough to generate many easy plus-one opportunities, and his ground game isn’t sturdy enough to make up for it. When his first serves come back, his results are close to tour average. But when the second serve comes back, he ranks at the very bottom of the table.

This scatterplot shows every player with at least ten charted matches over the last year. It compares each player’s win rate when their first serves come back with their results when second serves come back. Guys below the dotted line see relatively worse outcomes behind their second serve:

There’s no single limitation that is depressing Mensik’s second-serve results. The positive spin on that is that he has a lot of areas with room to improve. Even an average second serve–seemingly a reasonable goal for a man with such an imposing first–would probably make him a top-20 player.

The way forward

Nothing makes it easier to dream about a big future in tennis than a monster serve. Any list of overrated youngsters is going to be littered with powerful teens who remained too one-dimensional to convert all their aces into tournament victories.

That, I think, is the low-end forecast for Jakub Mensik. If he simply keeps doing what he’s doing, he could be a top-40 or top-50 player for a long time. His first serve is that good, and the rest of his game is adequate. He probably wouldn’t continue to win half of his top-ten meetings, since the game’s top players would have more time to figure him out.

On the other hand, again, he’s 19! The difference between his first- and second-serve results is a statistical oddity, which could mean either that he is uniquely one-dimensional, or that he has plenty of room to develop. The latter seems more likely. He may remain limited on return, but a second serve to match his first would make him near-unbreakable. That’s the recipe for a lot more top-ten wins, and possibly for a single-digit ranking of his own.

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Are Second Serves Mostly Useless?

Novak Djokovic loading up for some topspin

During the Australian Open, Challenger player (and Youtube star) Karue Sell made a bold statement:

Thank you, Karue, for posting this: It is always valuable to get specific claims about the game from the people who are trying to figure out how to win. Right or wrong, testable propositions like these help nudge our understanding in the right direction.

Now: Right or wrong?

Are second serves becoming mostly useless? A first look at the data says no–or, at least, they aren’t becoming any more useless than they were before. Here is second serve win percentage for tour-level matches since 1991:

The important thing here isn’t the trend. It’s the narrowness of the values. The difference between the lowest and highest ticks on this graph is only three percentage points, and half of that happened before the century turned. Strength and strategy may be different–we’ll get to that–but the results aren’t. If anything, second serves have become (modestly) less useless.

This trend holds up even when we tweak the parameters. Yes, the surface mix of the tour has changed since the 1990s. But if we look only at hard-court matches, there’s an even tighter range of yearly averages, between 48.9% and 51.2%. At Sell’s Challenger level, I only have data back to 2010. In that span, hard-court second-serve win rates have drifted less than a single percentage point, between 49.7% and 50.6%.

I can’t help but notice that Sell’s own Challenger-level second-serve win percentage is a healthy 52%. I’m sure it sometimes feels useless: The last match he played before making the comment was a qualifying-round loss in which he salvaged less than 40% of second-serve points. But despite his relatively small stature, he won more main draw second-serve points last year than Matteo Berrettini did–albeit against weaker competition.

Risk and reward

No one wants to settle for historical average. Inevitably, someone brought up the notion of two first serves:

No, two first serves are not the way. But Sell recognizes what might work. At least in theory, players should take more risk on second serves (and perhaps on firsts, as well), hitting bigger and winning more points at the cost of more doubles.

If tennis trends proceeded by opinion poll, I think we’d already see evidence of this. I certainly never see anyone argue that players should be more conservative with the second ball, unless they’re talking about a particular struggling player. But all that matters is what happens on court, and there’s no sign there of more double faults:

Again, the framing doesn’t matter. The numbers are about the same regardless of surface, and Challenger players have moved in the same direction. In fact, the 2025 Challenger rate so far is 9.8%, the first time that the minor leaguers have dipped below double digits.

To be clear, I wouldn’t expect any sudden moves here. A generation of players grows up learning certain serves and tactics, and there’s only so much they can do to change them. An equation might spit out that someone would win, say, 56% of second-serve points in exchange for accepting a 12% double-fault rate. But do athletes really have such fine-grained control of the risks they take? I suspect not, which means another generation may go by before we see a true “1 and 1.5” strategy.

Is 100 miles per hour a must?

How fast do second serves need to be? While I can’t imagine any player would turn down a triple-digit average, we’re nowhere near that level. The rightmost column shows the average second-serve speeds at the 2024 US Open for every player who reached the third round:

Only 4 of 32 averaged triple digits. Just five posted a mark at or above 96 miles per hour. The dominant tournament winner, Jannik Sinner, barely topped 90.

It’s possible that the sensors (or the balls, or the humid conditions, or pick your variable) resulted in low readings: US Open speeds are typically several miles per hour lower than Wimbledon speeds, even for the same players. But the gap isn’t enough to push more than a quarter of these guys over the magic number.

Still, Sell could be correct on the trend, if not on the detail. Maybe second serves are getting faster, or slower second serves are more likely to end in a point lost.

US Open data, though, suggests that second serves have stayed about the same. I have relevant data back to 2014, plus 2011. Splitting second serves into buckets of 100-plus miles per hour, 95-99, 90-94, and so on, it’s tough to find much of a trend:

(In case you’re wondering, the 2012-13 data has serve speeds, but no indication of first or second serves. Not very helpful here!)

Same story with win rates. As with the tour in general, the US Open has seen a steady percentage of second-serve points won. The next graph shows year-by-year win rates both overall and for the 85-89 mile-per-hour bucket, on the theory that if returners were feasting on relatively weak seconds, it would show up there:

While the 85-89 mph results are noisy, there’s not much to see here. The overall win rate in 2024 is almost identical to what it was 13 years earlier. There’s a bit of space between 85-89 mph second serves in 2011 and 2024, but still not much.

It’s certainly true that harder is better, and that hasn’t changed. At every one of these US Opens, the win rate of 100-plusses exceeded the win rate of sub-85s by at least five percentage points, and the gap rose as high as ten points at the 2020 Covid event. But we’ve yet to find much evidence for the notion that second serve speeds or results are any different than they were 10, 13, or even 30 years ago.

Are servers going to the forehand more often?

Finally, we can say… maybe?

I pulled all hard court matches since 2014 between right-handers from the Match Charting Project database. (Hard court, because it’s so much easier to run around second serves on clay; 2014, because that’s when the project started, so there’s not as much bias toward big-name players and matches; right-handers, because lefties, while fascinating, make things way more complicated.)

The charts classify serves into three categories: Wide, body, and T. Second serves to the “body” usually aren’t good: Those are serves that didn’t find a corner. In the men’s game, that’s 35-40% of seconds. It’s tough to tell from the chart–and sometimes even when watching a match–exactly which side the server targeted, because it is so easy for the returner to take a step or two around it and hit a forehand.

Servers are indeed more likely these days to find the forehand corner:

This isn’t an enormous move, but it seems like a real thing. If we throw out the 2020 Covid season, it would look like an even more dramatic shift just in the last few years.

However, more second serves to the forehand corner does not mean fewer second serves to the backhand corner. These extra forehand-targeted serves are coming at the expense of the mediocre “body” seconds. Servers drill the backhand corner 30% to 35% of the time, and that range hasn’t budged over the last decade.

I’d more inclined to say, then, that players have gotten a bit better. And they’ve chosen to use that improvement to keep returners off balance, aiming a few more second serves to the forehand side.

Are players too good from the back?

Sell’s theory is that more second serves are targeting the forehand, because the backhand is no longer such a weak side. We can use the same subset of MCP data to check how (right-handed) returners have fared against second serves to their backhand corner:

Again, 2020 is weird; other than that, we’re just looking at noise. (Or, possibly, the signature of a drunk blue M&M.) The long-term average of this stat is 50.6%, and in ten of the twelve seasons, the single-year number was within half a percentage point of that.

Backhand returns may have gotten stronger, but if so, serves are advancing at the same rate.

What gives?

Why would Karue identify trends that, for the most part, have so little evidence to support them?

First, the tour is getting stronger, at backhand returns and everything else. Some serves that would’ve gone unreturned in 2005 or 2015 are coming back today. As we’ve seen, servers are maintaining a balance. But it’s easy to suffer a few bad results and conclude that drastic changes have taken place.

Second, Karue himself played his best tennis last year. He cracked the top 300 for the first time and played a dozen Challenger main draws. That meant he faced stronger competition than ever. The Challenger tour is full of baseline battlers with sturdy backhands; there isn’t a huge gap between the return skill that Sell faces these days and the elite-level returning we watch on TV. Moving up from ITFs to Challengers means that some weapons don’t work anymore, and–especially for smaller guys–new tactics are needed.

I’d love to see Sell, or anyone else, give a serious trial to the “1 and 1.5” serve strategy. Hit seconds harder, attack the forehand more often, and accept more double faults. Karue might be right about what the future of second serves will look like, but we’re not there yet.

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The Inscrutable Magic of Jessica Pegula

Jessica Pegula playing defense at the 2022 US Open

Alright, alright, alright.

When I started writing these player-themed pieces more than a year ago, Jessica Pegula was at the top of my list. One of my goals is to demystify the factors that cause each player’s success, or lack thereof. Pegula has had plenty of success, but compared to her peers at the top of the game, it is difficult to say exactly why.

There’s no obvious calling card that intimidates opponents. Pegula doesn’t serve very hard, ranking in the middle of the pack at least year’s US Open with an average serve speed around 92mph and first serves at 99mph. She doesn’t hit many aces. She ranks just outside the top ten in hold percentage, largely because she cleans up on second serves. That’s her one standout, top-line stat: In the 52 weeks leading up to Indian Wells, she won 51% of second-serve points. Only four women have topped 50%, and only Iga Swiatek wins more.

Pegula’s return numbers are even more anonymous. She ranks 20th among the WTA top 50 in break percentage. Top 20 on both sides of the ball is outstanding and unusual, but again, hardly intimidating. Whether serving or returning, she isn’t particularly effective on break points. Not that she’s bad in that department, but clutch play doesn’t help us understand all the match wins.

But win matches she certainly does. The American has held a place in the top ten since June 2022, much of that time in the top five. She has won seven tour-level titles and reached finals at both the US Open and the year-end championships. Off a title in Austin, she’s on a seven-match winning streak going into today’s match against Elina Svitolina. Elo isn’t quite as excited about her performance, but even that metric places her seventh, only 16 points behind fifth-place Qinwen Zheng.

What, then, is Pegula doing so right? When a player gets better results than her tools seem to suggest, I tend to fall back on difficult-to-quantify assets like movement, anticipation, and the blackest box of all, tennis IQ. Pegula excels in all those categories. But can we do better?

Second thoughts

Let’s start with the second serves. Here’s a generic theory for you: second-serve win percentages are related to success rates on return. Few women have dominant second serves–remember that Pegula is one of only a handful who win more than half of those points–so especially if the returner puts the ball in play, the server is already on defense.

Indeed, there’s something of a relationship, though not a statistically strong one. This plot shows the WTA top 50 in both categories:

jpeg.jpg

Here’s a sentence I didn’t expect to write: Pegula and Sabalenka are almost identical in this pair of metrics. To go a step further, the cluster of players extending from Alexandrova in the lower left, to Sabalenka, then to Swiatek in the upper right, is disproportionately made up of big hitters. (The finesse players, along with the always unpredictable Jelena Ostapenko, are in the lower right.)

Yet by the standards of women’s tennis in the 2020s, Pegula is not a big hitter. It’s natural enough that she would equal Sabalenka’s return results, even if they get there in different ways. But second serves, too?

After watching Pegula’s quick dismissal of Xinyu Wang on Sunday, I thought I had the answer. While her second serves aren’t fast (79mph on average at last year’s US Open), they are precise. She doesn’t tee them up down the middle, and she manages to hit targets close to the service line. Location can be as valuable as raw speed, so that might explain how she gets the results of a bigger server.

Except… I can’t prove that she does any of that on a consistent basis. US Open scorers classify serve depth as “close to the line” or “not close to the line. Pegula merited a “close to the line” designation on 15% of her second serves, compared to a tournament average of 18%. She was slightly below average on first serves, too.

As for serve direction, it’s the same story. The Match Charting Project classifies each serve as one of three directions: wide, body, or down-the-tee. The average server hits one of the corners (wide or tee) with about 80% of their second serves. Pegula’s number is 74%. That’s not in itself bad–Venus Williams sports the same number–but it certainly doesn’t support my theory.

If there’s a quantifiable reason why Pegula wins all those second-serve points, it doesn’t look like we’ll find it in the second serve itself.

The match and the territory

Another eye-test hypothesis about Pegula: She doesn’t wait for the game to come to her. She stands as close to the baseline as she can get away with, both returning serve and in rallies. She doesn’t back up when faced with a deep drive or a high bounce. Depending on the shot, she’ll pick it up on a short hop or reach above her shoulder.

Not everyone is able to do this. For those who can, the advantages are clear. The earlier you hit the ball, the faster it gets back in your opponent’s court–and the less time they have to react. It’s power tennis for women without overwhelming power.

This style of play is particularly effective against opponents who aren’t particularly aggressive. Pegula’s losses this year have come against Madison Keys, Olga Danilovic, Ekaterina Alexandrova, and Linda Noskova: a quartet of heavy hitters who end points fast. Pegula lost just two matches on North American hard courts last summer, both to Aryna Sabalenka.

Against less free-swinging foes, the American takes away chances. Pegula doesn’t hit an overwhelming number of winners: 6% of her groundstrokes go untouched, in line with tour average. But her opponents do worse. In the Austin final, McCartney Kessler scored winners on just 2% of her shots from the baseline, half her usual rate. Pegula applied the same pressure to Xinyu Wang Sunday, slashing the Chinese player’s groundstroke-winner rate to 4% from a career average of 7%.

Again, these are stats that invoke parallels with a different style of player. The best way to prevent winners is to hit winners of your own, or at least end the point trying. That’s the Keys/Alexandrova/Ostapenko/etc playbook. Yet by Aggression Score, a metric that puts those ball-bashers on top, Pegula is below average, keeping company with the likes of Emma Navarro and Mirra Andreeva.

Deep research

Maybe you’re convinced that this explains a lot of Pegula’s success. She hugs the baseline, cuts off angles, and takes away opportunities for all but the most aggressive players to find openings of their own.

Still, I’d like more support from the numbers. Positioning is tricky to quantify, so I want to focus on one specific situation. What happens when the American is faced with a very deep service return?

Deep returns essentially erase the server’s advantage, neutralizing the point with one swing. The server usually needs to take a step or two back, and unless it’s a perpetual gambler like Ostapenko, she won’t try anything flashy for at least one more shot. Pegula doesn’t aim to end the point, either, but she’s less likely to concede territory. While that doesn’t allow her to seize the advantage, she’s careful not to hand too much of an edge to the returner.

Yet… nope. The next table shows how the ten players with the most hard-court data since 2022 handle deep second-serve returns: How often they get the next ball back in play (“3rd-inPlay”), how often those balls in play result in points won (“inPlay W%”), and how often they win points against deep returns, even considering the ones they didn’t get back (“vsDeep W%”).

Player            3rd-inPlay  inPlay W%  vsDeep W%  
Iga Swiatek            84.2%      59.8%      50.4%  
Aryna Sabalenka        77.5%      63.5%      49.2%  
Karolina Muchova       84.2%      56.3%      47.4%  
Paula Badosa           84.2%      54.6%      45.9%  
Elena Rybakina         79.5%      57.5%      45.7%  
Daria Kasatkina        85.5%      52.2%      44.6%  
Coco Gauff             83.6%      53.2%      44.5%  
Jasmine Paolini        82.7%      53.7%      44.4%  
Jessica Pegula         81.9%      53.2%      43.6%  
AVERAGE                81.8%      53.0%      43.4%  
Qinwen Zheng           76.5%      52.6%      40.2%

Pegula is almost exactly average, which makes her less effective against deep second-serve returns than most other top players. (The average considers all players, not just those listed, which is why it’s so close to the bottom.) Sticking to the baseline might still be the best solution for her, but it doesn’t win her an unusually high number of points.

This is a lot of negative results for one post. Pegula is close to the best in the business at turning her second serve into points won. But it’s not because she hits her seconds deep, or because she keeps the ball away the returner, or because she handles deep returns unusually well.

So we’re more or less back where we started. The American does a lot of things well, or at least well enough that they are not liabilities. Among top 50 players, she is average or better in nearly every category, close to the top ten in a few. By my groundstroke potency metrics, FHP and BHP, she does even better: She ranks among the top 20 in both, one of the few players to do so.

That, apparently, is good enough for a place in the top five. With better, finer-grained stats, we might be able to isolate how Pegula turns court position into victory. For now, we can appreciate how she holds her own against opponents with more fearsome weapons. Her personal brand of flexible shotmaking is certainly working, whether we understand it or not.

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The Second-Serve Woes of Arthur Fils

The outcome of this point depends a great deal on whether Arthur Fils is about to hit a first or second serve.

Arthur Fils is a bit of a forgotten prospect. A year younger than Carlos Alcaraz and two years older than Joao Fonseca, he isn’t considered to have the awe-inspiring talent of either. Then again, who does? By any other standard, the 20-year-old Frenchman has made tremendous progress. Standing at #19 on the ATP computer, he’s the top-ranked player under 21, and he’s even within the top five of under-23s.

There’s no secret to the Fils game. He hits hard, smacking serves over 130 miles per hour and occasionally connecting with a forehand that might even cause Fonseca’s eyebrow to twitch. In Saturday’s Davis Cup match against Thiago Seyboth Wild, he scored 11 aces in only 54 service points. He won 29 of 32 points when he landed his first serve.

The Frenchman has plenty more to his game, as well. He is sturdy off both wings, unafraid to battle from the baseline. He rates +5 in Forehand Potency, hardly a tour-leading number, but better than the likes of Daniil Medvedev and Holger Rune. By the same metric, his backhand is neutral. That’s another number that looks better in context: He won’t win any awards, but the shot isn’t holding him back.

At first glance, then, his biggest challenge is making inroads on return. He has won 36.2% of return points over the last 52 weeks, a number just below the usual minimum for an elite player. It ranks him above Rune, Hubert Hurkacz, and Taylor Fritz, but behind most of his fellow top-20 players. It isn’t an obstacle to cracking the top ten, though, as Hurkacz and Fritz have shown.

Fils’s problem now is what happens when he misses that big first serve. Among the ATP top 50, he ranks 16th in first-serve points won, just ahead of Karen Khachanov. By second-serve points won, he ranks a dire 43rd, several places down the list from Sebastian Baez. Even in Saturday’s Davis Cup rout, the Frenchman failed to win half of his second-serve points.

What’s going wrong? Is it something that young players tend to improve? What does a second-serve weak point say about a prospect’s future trajectory?

Second to many

Let’s get a sense of the typical relationship between first- and second-serve win rates. This scatterplot shows the ATP top 50 over the last 52 weeks:

Players who are successful behind one serve are generally successful behind both, with Jannik Sinner leading the way in the upper-right corner. Carlos Alcaraz and Novak Djokovic rank among the second-serve win rate leaders, though their first-serve results aren’t as strong. Grigor Dimitrov and Giovanni Mpetshi Perricard pop out as men with effective first serves who don’t do as much behind the second.

Fils hardly sticks out as a disaster, especially with Alexander Bublik there to distract us. Still, for a man who can win more than three-quarters of his first-serve points, he sits in the wrong part of this grid. There’s virtually no difference between his and Ben Shelton’s first-serve results, yet the American wins five percentage points more often with his second serves. Shelton is top-five in hold percentage, while Fils languishes outside the top 30, despite a near-identical first-serve success rate.

The diagnosis

It’s one thing to say that a player doesn’t win enough points behind his second serve. Can we figure out why?

Start with two things it’s not. Fils commits more double faults than average: 4.1% of serve points versus the typical top-50 rate of 3.4%. But even when he lands his second serve, the results are disappointing. Instead of 43rd among the top 50, he’s 37th. Fewer doubles might be nice, but they would barely move the needle.

We can also cross particularly soft second serves off the list. At the US Open last year, Fils averaged 115 miles per hour on first serves and 92 miles per hour on seconds. That’s a gap of 23 miles per hour–exactly in line with the norm among players who reached the third round. Jannik Sinner averaged 91 miles per hour with his second serves, so raw speed isn’t the problem.

That leaves us with where the second serves are landing. Unscientifically, I get the impression that Fils’s second serves don’t land particularly deep. Khachanov, for instance, hits a bog-standard topspin second, yet it’s fine because he consistently drops it deep in the backhand corner. The Frenchman sometimes hits that serve, but just as often his not-enough-topspin delivery lands in the middle of the box. In 2025, against this field, that’s not going to cut it.

Match Charting Project data can’t tell us how deep the serves are landing, but it does tell us what direction they go:

           Dc-Wide  Dc-Body   Dc-T   Ad-T  Ad-Body  Ad-Wide  
Fils 2nds    17.5%    38.1%  44.4%  11.3%    20.4%    68.3%

First, the Frenchman rarely goes for the forehand. With a really good second serve, that’s smart. But with less imposing strikes, it gives opponents options. Last week I linked to an analysis of Alcaraz’s loss to Djokovic in Melbourne, where Alcaraz went to the backhand side on second after second–probably too often. That gave Novak the flexibility to position himself differently and play the returns more aggressively. Fils is making a similar offer to everyone he plays, especially on the ad side.

Second, that’s a lot of deuce court serves down the middle. “Body” is misleading–usually when we talk about body serves, we mean the really good ones, flying 125 miles per hour at the returner’s left hip. That’s not what’s happening here. A more appropriate name for the category is something less inspiring, like “serves that aren’t in a corner.” Whether the returner has move a couple steps or none at all, those are booming forehand returns waiting to happen.

Here are the directional breakdowns of a few men with strong second-serve results, for comparison:

           Dc-Wide  Dc-Body   Dc-T   Ad-T  Ad-Body  Ad-Wide  
Fils         17.5%    38.1%  44.4%  11.3%    20.4%    68.3%  
Shelton      27.3%    40.3%  32.4%  21.6%    35.0%    43.4%  
Djokovic     35.5%    38.8%  25.6%  30.6%    27.2%    42.2%  
Sinner       14.1%    61.5%  24.4%  15.0%    49.8%    35.1%

Both Shelton and Djokovic mix things up a lot more. Sinner does everything I’ve just criticized about Fils and, at least in New York last fall, he did it at the same speed. Sheepish grin emoji. Surely there’s more going on there, but we’ll have to save it for another day.

In development

In one way, clear weaknesses are a good thing. It’s easier to identify a clear target area for practice than to vaguely aim to get a little better at everything. I’m sure Fils and his team are aware that he should get more out of his second serve, and we’ll see him change things up.

The question, then, is if those efforts are likely to bear fruit. Many players struggle to meaningfully improve their stats once they’ve established themselves on tour. It’s hard enough to tread water. Opponents figure out how to counteract their weapons, age and wear-and-tear take their toll, and–if the player is lucky enough to climb the rankings–the average opponent in later rounds is stronger.

Fils has compared himself to Jo-Wilfried Tsonga. Tsonga never had a sub-50% second-serve win rate, but he did have middling figures around 51.5% in his first two years on tour. On the other hand, Tsonga was a late bloomer: He was barely playing Challengers when he was 20.

For a more comprehensive answer, I found 75 men who played full seasons on tour at age 20 since 1991. All but five of them eventually bettered their age-20 second-serve win rate, and the average improvement was 2.7 percentage points. If that holds true for Fils, he’ll peak around 52% on second serves. That’s not bad, though I suspect he would be disappointed if he never does better than that. It would still be an underperformance for someone with his first-strike weapons.

Indeed, the one-third of these players who posted sub-50% second-serve win rates at age 20 improved more than the larger population. They gained 3.4 percentage points. Among them are some names that might inspire even greater feats from the young Frenchman:

Player           Age 20 2ndW%  Peak  Peak 2ndW%    
Andrey Rublev           49.3%  2020       53.9%    
Nicolas Almagro         49.1%  2012       55.1%    
Sam Querrey             48.2%  2015       54.1%    
Tommy Haas              47.7%  2006       54.8%

All four won fewer second-serve points at age 20 than Fils did in 2024. Each one fully shored up the weakness– at least for one season. 54% isn’t elite, but it’s more than good enough, especially when paired with a top-notch first serve.

To be clear, I’m not forecasting a Haas-like, seven-point improvement for Fils. Repairing weak points at tour level is exceptionally difficult, and even the three-percentage-point norm will take a lot of work. It is nonetheless a challenge the Frenchman will need to undertake. He has come a long way on the back of a big first serve, but to breach the top ten, he’ll need a more well-rounded attack.

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The Locked-Down Serve of Jannik Sinner

It’s all business for Jannik Sinner, and business is good.

There are a lot of things we could talk about after Jannik Sinner’s latest display of dominance. With a second Australian Open title, his exceptional span of hard court performance has stretched to 13 months, and according to my Elo ratings, only eight players in the Open era have ever been better than the Italian is right now.

A year ago, I wrote that Yes, Jannik Sinner Is This Good. If anything, he has improved since then. He holds serve more often than anyone on tour–yes, even more than Giovanni Mpetshi Perricard. Yet he is far from one-dimensional. He couples the serve with elite groundstrokes on both wings. He breaks serve more often than all but six players on the circuit.

One particular aspect of Sunday’s victory stands out. In three sets, spanning 15 service games, Sinner did not face a single break point.

Zero break points faced is one of those stats that sounds really good–then it gets even better the closer you look. Alexander Zverev a top-ten returner. He breaks nearly one-quarter of his opponents’ service games. He earns approximately 0.6 break points per game, or three per set. In three sets, the Italian didn’t allow him one.

Every season there are a couple hundred matches in which the winner doesn’t face a break point. Yet most of those are short best-of-threes, many of them involving overmatched wild cards and qualifiers. In 2024, there were only five matches in which a top-ten player failed to generate a single break point over more than ten return games. Twice the victim was Hubert Hurkacz, probably the weakest returner among the elites. Another hapless outing came from Casper Ruud, who was held to zero by Zverev at the Tour Finals.

The other two standout matches belong to Sinner. In last year’s Australian Open semi-final, then again in the Shanghai title match, he shut down Novak Djokovic. The only recent precedents for Sinner’s plastering of Zverev are the Italian’s own performances.

What can we learn from the latest episode of the Sinner show?

Situational awareness

Twelve months ago, Sinner was developing a reputation as an escape artist. He beat Daniil Medvedev in a five-set Melbourne final, winning just one more point than the Russian. He snuck past Djokovic twice in November 2023, once winning exactly the same number of points, a second time despite winning four points fewer.

Sinner had a knack for erasing break points. Most players are less successful facing break point than on other service points, because stronger returners generate more break points. (Also, break points tend to crop up amid rough patches, at least for players human enough to occasionally slump.) The Italian, though, saved break points at a better clip than his other service points. He hit bigger at those moments, and it worked.

Recognizing that trend a year ago, I tempered the celebration with a dose of reality:

…I can tell you what usually happens after a season of break-point overperformance: It doesn’t last. Taking over 2,600 player-seasons since 1991, 582 (21.7%) of players saved more break points than they won serve points overall. 183 (6.8%) matched Sinner’s mark of saving at least two percentage points more than their serve-points-won rate.

That sound you hear? That’s Darren Cahill laughing at us. Sinner didn’t quite continue at the same pace, but he still serves better facing break point than otherwise. He wins a tour-leading 71.5% of serve points overall, and the number climbs to 72.5% when an opponent has him on the ropes.

(71.5% is circuit-best, but 72.5% is not: Ben Shelton stands at 73.1%. No one told Jannik, though. In their semi-final, Sinner won 6 of 13 break points against the Shelton serve.)

Of course, this specific skill didn’t come into play on Sunday. Sinner didn’t have break-point-faced results, because he didn’t face any break points. If you have an even bigger weapon to deploy at key moments, why wait until it’s absolutely necessary?

Beyond the escape room

Some players–especially left-handers–are more effective serving to the ad court than the deuce court. That helps them save break points, because most break points (30-40 and ad-out) take place in the ad court.

Sinner is right-handed. Across the 250-plus matches for which I have sequential point-by-point data, he is slightly more effective serving to the deuce court:

COURT    A%   SPW%  
Deuce  7.6%  66.6%  
Ad     6.5%  66.3%

The different in points won isn’t anything to build a strategy around, but the ace-rate gap suggests there might be a meaningful difference.

In Melbourne, the success rates took on a new look. Based on the five Australian Open matches in the Match Charting Project database, here are the same metrics:

COURT    A%   SPW%  
Deuce  8.9%  74.6%  
Ad     9.4%  70.8%

The ace rates flipped, but holy four percentage points! 70.8% serve points won is very good, better than anyone else on tour over the last 52 weeks. 74.6%, though: That’s from another planet. It’s better than John Isner’s best season.

It may be a fluke. After all, it’s just five matches, and Sinner’s deuce- and ad-court results were nearly identical in 2024. But I suspect there’s strategy at work here.

Up to eleven

I noted last year that Sinner served bigger facing break point than he did otherwise: 125 miles per hour compared to 122. What about other key situations?

At the US Open last year, the Italian showed some deuce-court preference, winning 72.7% of deuce-court points compared to 71.3% on the ad side. It wasn’t a matter of power, as he averaged almost identical speeds (117.9 to 117.7 mph) in the two directions.

Speed differences turn up at a more granular level. Here are Sinner’s first-serve speeds at the most common point scores he faced:

Score    MPH  
15-30  121.0  
40-40  120.3  
40-15  120.0  
0-15   119.7  
30-30  119.4  
40-30  118.0  
30-15  117.7  
30-0   117.0  
15-0   116.6  
0-0    116.6  
15-15  115.8  
40-0   113.0

(Yes, I know it’d be nice to have 30-40, 40-AD, 15-40, and so on. But this is Sinner we’re talking about. He didn’t face many of those.)

With the exception of 40-15, this list is an awfully good approximation of point scores listed by importance. With more at stake, the Italian hit harder. There’s no apparent trade-off, either. He made more first serves than average at 15-30 and deuce, even with the faster strikes.

The point is that when Sinner feels the need to go big, he has the ability to do so. Most players don’t: Their results don’t get better in critical moments, either because they’re already maxing out their skills on routine points, or because their opponents can raise their levels, as well. But the Australian Open champ has more in the tank than anybody who dares to stand across the net from him.

As the Italian rose through the rankings, he saved that extra oomph for break point. Now that he enters every match as the favorite, he can be even more aggressive. By serving harder at 15-30, or 30-all, Sinner probably doesn’t risk overexposure. With the possible exception of Alcaraz or a time-traveling Djokovic, no one can do much with an accelerated Sinner first serve–even if they’ve seen one recently.

The full arsenal

Put all of this together, and it’s hard to avoid the conclusion that Sinner will continue to climb the all-time list. In terms of peak level, Andy Murray is next:

Rank  Player          Peak Elo  
1     Bjorn Borg          2473  
2     Novak Djokovic      2470  
3     John McEnroe        2442  
4     Ivan Lendl          2402  
5     Roger Federer       2382  
6     Rafael Nadal        2370  
7     Jimmy Connors       2364  
8     Andy Murray         2347  
9     Jannik Sinner       2325  
10    Boris Becker        2320

Sinner wins more service points than anyone else in the game–even when he isn’t particularly trying. At the same time, he is an elite returner.

We’ve seen a few players with a similar service profile. Pete Sampras also had a knack for coming through at the end of sets. But he leaned on his tiebreak skill more than Sinner ever will, because his return game was mediocre. Roger Federer was better: a dominant–and clutch–server, and a more competitive returner than Pistol Pete. Nick Kyrgios had one of the most electric serves in the game’s history, coupled with the ability to focus at critical moments. Yet he was the most one-dimensional of the bunch. His return would have held him back even if he had stayed healthy.

Sinner has all the serve dominance without the drawbacks. He has no apparent weakness. He won’t win all the time, and he won’t stay on top forever, but at the moment, it’s hard to see how anyone will stop him.

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