Podcast Episode 14: Wimbledon Preview

Episode 14 of the Tennis Abstract Podcast is Carl Bialik’s and my Wimbledon preview! We highlight the favorites, the overrated, and the underrated, along with a look at some of the most intriguing matchups. Along the way, we talk about the difficult of making grass court forecasts, and speculate about how players’ consistency changes with age.  Enjoy!

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The Men Are Old, and The Best Men Are Even Older

It’s been one of the main talking points in men’s tennis for years now: The sport is getting older. Every year, a bigger slice of Grand Slam draws are taken up by thirty-somethings, and now, the entire big four has entered their fourth decades.

I don’t want to belabor the point. But my interest was piqued by an observation from commentator Chris Fowler this week:

When we talk about the sport getting older, this is what we really mean — the best guys are getting up in years.

When we calculate the average age of a draw, or the number of 30-somethings, we weight every player equally. Democratic as it is, it gives most of the weight to guys who are looking for flights home before middle Sunday. As substantial as the overall age shift has been over the last decade, the shift at the top of the game has been even more dramatic.

To quantify the shift, I calculated what I’ll call the “projected winner age” (PWA) of every Wimbledon men’s field from 1991 to 2017. This captures in one number the notion that Fowler is hinting at. We take a weighted average of all 128 men in the main draw, weighted by their chances of winning the tournament, as determined by grass-court Elos at the start of the event.

For example, last year’s Wimbledon men’s draw had an average age of 28.5 years, but a projected winner age of 30.0. We don’t yet know the exact average age of this year’s draw (it looks to be about the same, maybe a tiny bit younger), but we can already say that the PWA is 31.4.

An observer a decade ago would’ve thought such a number was insane. Here are the average ages and PWAs for the last 27 Wimbledons men’s events:

As recently as 2011, there wasn’t much difference between average age and PWA. Until 2015, the difference had never been greater than two years. Now, the difference is almost three years, and the point of comparison–average age–is nearly its own all-time high.

A lot of this, of course, is thanks to the big four. Even as the aging curve has shifted, allowing for late bloomers such as Stan Wawrinka, the biggest stars of the late ’00s–Roger Federer and Rafael Nadal–have declined even less than the revised aging curve would imply. In a sport hungry for new winners, we might have to settle for winners who are newly in their 30s.

Measuring the Impact of Wimbledon’s Seeding Formula

Unlike every other tournament on the tennis calendar, Wimbledon uses its own formula to determine seedings. The grass court Grand Slam grants seeds to the top 32 players in each tour’s rankings, and then re-orders them based on its own algorithm, which rewards players for their performance on grass over the last two seasons.

This year, the Wimbledon seeding formula has more impact on the men’s draw than usual. Seven-time champion Roger Federer is one of the best grass court players of all time, and though he dominated hard courts in the first half of 2017, he still sits outside the top four in the ATP rankings after missing the second half of 2016. Thanks to Wimbledon’s re-ordering of the seeds, Federer will switch places with ATP No. 3 Stan Wawrinka and take his place in the draw as the third seed.

Even with Wawrinka’s futility on grass and the shakiness of Andy Murray and Novak Djokovic, getting inside the top four has its benefits. If everyone lives up to their seed in the first four rounds (they won’t, but bear with me), the No. 5 seed will face a path to the title that requires beating three top-four players. Whichever top-four guy has No. 5 in his quarter would confront the same challenge, but the other three would have an easier time of it. Before players are placed in the draw, top-four seeds have a 75% chance of that easier path.

Let’s attach some numbers to these speculations. I’m interested in the draw implications of three different seeding methods: ATP rankings (as every other tournament uses), the Wimbledon method, and weighted grass-court Elo. As I described last week, weighted surface-specific Elo–averaging surface-specific Elo with overall Elo–is more predictive than ATP rankings, pure surface Elo, or overall Elo. What’s more, weighted grass-court Elo–let’s call it gElo–is about as predictive as its peers for hard and clay courts, even though we have less grass-court data to go on. In a tennis world populated only by analysts, seedings would be determined by something a lot more like gElo and a lot less like the ATP computer.

Since gElo ratings provide the best forecasts, we’ll use them to determine the effects of the different seeding formulas. Here is the current gElo top sixteen, through Halle and Queen’s Club:

1   Novak Djokovic         2296.5  
2   Andy Murray            2247.6  
3   Roger Federer          2246.8  
4   Rafael Nadal           2101.4  
5   Juan Martin Del Potro  2037.5  
6   Kei Nishikori          2035.9  
7   Milos Raonic           2029.4  
8   Jo Wilfried Tsonga     2020.2  
9   Alexander Zverev       2010.2  
10  Marin Cilic            1997.7  
11  Nick Kyrgios           1967.7  
12  Tomas Berdych          1967.0  
13  Gilles Muller          1958.2  
14  Richard Gasquet        1953.4  
15  Stanislas Wawrinka     1952.8  
16  Feliciano Lopez        1945.3

We might quibble with some these positions–the algorithm knows nothing about whatever is plaguing Djokovic, for one thing–but in general, gElo does a better job of reflecting surface-specific ability level than other systems.

The forecasts

Next, we build a hypothetical 128-player draw and run a whole bunch of simulations. I’ve used the top 128 in the ATP rankings, except for known withdrawals such as David Goffin and Pablo Carreno Busta, which doesn’t differ much from the list of guys who will ultimately make up the field. Then, for each seeding method, we randomly generate a hundred thousand draws, simulate those brackets, and tally up the winners.

Here are the ATP top ten, along with their chances of winning Wimbledon using the three different seeding methods:

Player              ATP     W%  Wimb     W%  gElo     W%  
Andy Murray           1  23.6%     1  24.3%     2  24.1%  
Rafael Nadal          2   6.1%     4   5.7%     4   5.5%  
Stanislas Wawrinka    3   0.8%     5   0.5%    15   0.4%  
Novak Djokovic        4  34.1%     2  35.4%     1  34.8%  
Roger Federer         5  21.1%     3  22.4%     3  22.4%  
Marin Cilic           6   1.3%     7   1.0%    10   1.0%  
Milos Raonic          7   2.0%     6   1.6%     7   1.7%  
Dominic Thiem         8   0.4%     8   0.3%    17   0.2%  
Kei Nishikori         9   1.9%     9   1.7%     6   1.9%  
Jo Wilfried Tsonga   10   1.6%    12   1.4%     8   1.5%

Again, gElo is probably too optimistic on Djokovic–at least the betting market thinks so–but the point here is the differences between systems. Federer gets a slight bump for entering the top four, and Wawrinka–who gElo really doesn’t like–loses a big chunk of his modest title hopes by falling out of the top four.

The seeding effect is a lot more dramatic if we look at semifinal odds instead of championship odds:

Player              ATP    SF%  Wimb    SF%  gElo    SF%  
Andy Murray           1  58.6%     1  64.1%     2  63.0%  
Rafael Nadal          2  34.4%     4  39.2%     4  38.1%  
Stanislas Wawrinka    3  13.2%     5   7.7%    15   6.1%  
Novak Djokovic        4  66.1%     2  71.1%     1  70.0%  
Roger Federer         5  49.6%     3  64.0%     3  63.2%  
Marin Cilic           6  13.6%     7  11.1%    10  10.3%  
Milos Raonic          7  17.3%     6  14.0%     7  15.2%  
Dominic Thiem         8   7.1%     8   5.4%    17   3.8%  
Kei Nishikori         9  15.5%     9  14.5%     6  15.7%  
Jo Wilfried Tsonga   10  14.0%    12  13.1%     8  14.0%

There’s a lot more movement here for the top players among the different seeding methods. Not only do Federer’s semifinal chances leap from 50% to 64% when he moves inside the top four, even Djokovic and Murray see a benefit because Federer is no longer a possible quarterfinal opponent. Once again, we see the biggest negative effect to Wawrinka: A top-four seed would’ve protected a player who just isn’t likely to get that far on grass.

Surprisingly, the traditional big four are almost the only players out of all 32 seeds to benefit from the Wimbledon algorithm. By removing the chance that Federer would be in, say, Murray’s quarter, the Wimbledon seedings make it a lot less likely that there will be a surprise semifinalist. Tomas Berdych’s semifinal chances improve modestly, from 8.0% to 8.4%, with his Wimbledon seed of No. 11 instead of his ATP ranking of No. 13, but the other 27 seeds have lower chances of reaching the semis than they would have if Wimbledon stopped meddling and used the official rankings.

That’s the unexpected side effect of getting rankings and seedings right: It reduces the chances of deep runs from unexpected sources. It’s similar to the impact of Grand Slams using 32 seeds instead of 16: By protecting the best (and next best, in the case of seeds 17 through 32) from each other, tournaments require that unseeded players work that much harder. Wimbledon’s algorithm took away some serious upset potential when it removed Wawrinka from the top four, but it made it more likely that we’ll see some blockbuster semifinals between the world’s best grass court players.

Nick Kyrgios and the First Fifty Matches

When Nick Kyrgios lost the Wimbledon quarterfinal to Milos Raonic yesterday, he was playing his 50th career match at the Challenger level or above. Round numbers invite big-picture analysis, so let’s see how Kyrgios stacks up to the competition at this early milestone.

When Monday’s rankings are released, Nick will debut in the top 100, all way up to #66. Only Rafael Nadal (61), Gael Monfils (65), and Lleyton Hewitt (65) have been ranked higher at the time of their 51th Challenger-or-higher match.  Roger Federer was #93, Novak Djokovic was #128, and Jo Wilfried Tsonga was #314. Of the current top 100, only ten players reached a double-digit ranking by their 51st match.

The wealth of ranking points available at Grand Slams have played a big part in Kyrgios’s rise, but they don’t tell the whole story. He has won 36 of his first 50 matches, equal to the best of today’s top 100. Nadal went 36-14, and next on the list is Djokovic and Santiago Giraldo (who played almost all Challengers) at 34-16. Most of Nick’s wins before this week came at Challengers, and he has won four titles at the level.

No other active player won four Challenger titles in his first 50 matches. Eight others, including Djokovic, Tsonga, Stanislas Wawrinka, and David Ferrer, won three. All of them needed more events at the level to win three titles than Kyrgios did to win four.

Nick’s short Challenger career is another indicator of a bright future. He has only played nine Challenger events, and with his ranking in the 60s, he may never have to play one again. As I’ve previously written, the best players tend to race through this level: Federer, Nadal, and Djokovic all played between eight and twelve Challengers. It’s a rare prospect that makes the jump in fewer than 20 events, and when I researched that post two years ago, more than half of the top 100 had played at least 50 Challengers.

One category in which the Australian doesn’t particularly stand out is age. When he plays his 51st match, he’ll a couple of months past his 19th birthday. Roughly one-quarter of the current top 100 reached that match total at an earlier age. Nadal, Richard Gasquet, and Juan Martin del Potro did so before their 18th birthday, while Djokovic, Hewitt, and Bernard Tomic needed only a few more weeks beyond that.

Without knowing how Kyrgios would’ve performed on tour a year or two earlier, it’s tough to draw any conclusions. His 36-14 record at 19 certainly isn’t as impressive as Rafa’s equivalent record at 17.

Cracking the top 100 at 17 or 18 is a much better predictor of future greatness than doing so at 19, but as the tour ages, 19 may be the new 16. Grigor Dimitrov didn’t enter the top 100 until he was three months short of his 20th birthday, while Dominic Thiem and Jiri Vesely were still outside the top 100 on their 20th birthdays. Among his immediate cohort, Kyrgios stands alone: No other teenager is ranked within the top 240.

As predictive measures go, Nick’s Wimbledon performance–built on his poise under pressure–is the best sign of them all. Only seven active players have reached a Grand Slam quarterfinal as a teenager, and four of them–Fed, Rafa, Novak, and Lleyton–went on to reach #1. (The other three are Delpo, Tomic, and Ernests Gulbis.)

For a player with only fifty matches under his belt, that’s excellent company.

Nick Kyrgios, Young Jedi of the Tiebreak

At Wimbledon this year, 19-year-old rising star Nick Kyrgios has shown himself to be impervious to pressure. In his second round upset of Richard Gasquet, he tied a Grand Slam record by surviving nine match points. Against Rafael Nadal, he withstood perhaps the best clutch player in the game. Despite Nadal’s stature as one of the best tiebreak players in the game, the Australian won both of the tiebreaks they contested.

As I’ve shown in other posts, tiebreaks are–for most players–toss-ups. Better players typically win more than 50% of the tiebreaks they play, but that’s because they’re better players, not because they have some tiebreak-specific skill. Only a very few men–Nadal, Roger Federer, and John Isner are virtually alone among active players–win even more tiebreaks than their non-tiebreak performance would indicate.

Kyrgios is making a very strong case that he should be added to the list. In his career at the ATP, ATP qualifying, and Challenger levels, he’s won 23 of 31 tiebreaks, good for an otherworldly 74% winning percentage. Isner has never posted a single-season mark that high, and Federer has only done so twice.

Nick isn’t playing these matches against weaker opponents, and he isn’t cleaning up in non-tiebreak sets. (Too many scores like 7-6 6-1 might suggest that he shouldn’t have gotten himself to 6-6 in the first place.) Based on Kyrgios’s serve and return points won throughout each match, a tennis-playing robot would have had a 52% chance of winning each tiebreak.

Given those numbers, it’s extremely likely that Kyrgios is one of the outliers, a player who wins many more tiebreaks than expected. There’s only a 1% chance that his excellent winning percentage is purely luck. We can be 95% sure that a tiebreak winning percentage of 58% or better is explained by skill, and 90% sure that his tiebreak skill deserves at least a winning percentage of 62%.

Either one of these more modest figures would still be excellent. Milos Raonic, his quarterfinal opponent and a player who represents an optimistic career path for Kyrgios’s next few years, has posted a 58% tiebreak winning percentage at tour level. Tomorrow’s match won’t be enough to prove which player is better in these high-pressure moments, but given each man’s playing style, it’s almost certain that we’ll see Kyrgios tested in another batch of tiebreaks.

Unbroken Grand Slam Quarterfinalists

Through the first four rounds at Wimbledon, Roger Federer‘s serve has not been broken. In that span, he has faced nine break points, including only four in his last three matches.

Since 1991–the first year for which match stats are available–this is only the 8th time a player reached the quarters of a men’s major without losing serve. Only Federer in 2004 and Ivo Karlovic in 2009 have done so at Wimbledon. Federer and Nadal are the only players to have done so more than once. (Fed was also unbroken through four matches in Melbourne last year, and Rafa accomplished the feat  at the 2010 and 2013 US Opens.)

Roger’s nine break points faced are a bit less impressive. More than 5% of the 752 Grand Slam quarterfinalists since 1991 have allowed fewer, including Federer himself on several occasions. He allowed only three break points at Wimbledon in 2007, and only four at three other majors.

Dominant as such a performance is, it’s less clear whether it has any predictive value. A major confounding factor is quality of competition–would anyone expect Paolo Lorenzi or Santiago Giraldo to break Federer on grass? While he built on these superb serving performances and went on to win the title at Wimbledon in 2004 and 2007, he failed to do so at the three majors when he allowed only four break points through this stage of the tournament.

Without accounting for player quality, there is a weak negative correlation between matches won at the event and break points (and breaks) allowed. (For instance, for matches won and break points allowed in the first four matches, r = -0.25. Excluding Roland Garros, r = -0.27.) In other words, if all you know about two players is how many break points they faced in the first four rounds, bet on the guy who faced fewer.

But it’s a weak relationship, and when player quality is taken into account, it vanishes to almost nothing. Eight of the 24 players who were broken one or fewer times in the first four rounds went on to win the title, but I suspect that has more to do with the prevalence of Rafa, Roger, and Pete Sampras–the best players are most likely to go unbroken, and the best players are most likely to go deepest at Slams.

When the best players struggle on serve in early rounds, it’s hardly a death knell for their title chances. Only four times in Fed’s 31 previous hard- and grass-court Slam quarterfinal runs has he been broken more than six times before the quarters, and he won the tournament one two of those four occasions. He’s surely happy to be into the quarterfinals this week with a minimum of fuss, but the fuss level only says so much about how happy he’ll be come Sunday.

Teenagers, Thirty-Somethings, and Americans at Grand Slams

I’ve put together a few reports showing how age distributions and US presence have changed over the years at Grand Slams.  Let’s start with player age.

The average age of players in the Wimbledon men’s singles draw is 27.7 years, which is just short of the all-time record, 27.8, set at Roland Garros last month, and equal to last year’s figure at Wimbledon. There are two teens in the draw (up one from last year), and 34 thirty-somethings, which is tied for third-most since 1982.

This report shows the complete year-by-year breakdown for the last 30 years’ worth of men’s slam draws.

The average age in the Wimbledon women’s draw is also very high by historical standards.  At 25.2 years, it’s tied with this year’s French Open and 2012 Wimbledon for the highest ever.  43-year-old Kimiko Date Krumm moves the needle all by herself; without her, the average would be 25.0, still considerably higher than any other pre-2010 slam.

There are ten teenagers in the draw, which is very low for the WTA, but safely above the all-time low of 7, set at Wimbledon two years ago. The total of 16 players aged 30 or over is good for third-most of all time, behind this year’s and last year’s French Opens.

Here’s the WTA report showing these numbers for each slam in the last 30 years.

(All of the figures above for 2014 Wimbledon could change slightly if more lucky losers are added to the draw.)

I also put together a couple of reports showing the number of Americans in each slam draw, broken down by direct entrants, qualifiers, lucky losers, and wild cards, along with the top seed, the number of seeds (and top 16 seeds), plus the number of Americans in each round: