Podcast Episode 7: Champion Simona, King Rafa, and Memories of Pico

In the Episode 7 of the Tennis Abstract Podcast, Carl Bialik and I cover a lot of ground, from Simona Halep’s Madrid title and Kristina Mladenovic’s recent outspokenness, to Rafael Nadal’s unbeaten streak and Dominic Thiem’s rising status as a clay-court contender, along with the inevitability that someone born in the 1990s will eventually win a big ATP title.

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Dominic Thiem played Davis Cup in Barcelona. Sort of…

This is a guest post by Peter Wetz.

Last week Dominic Thiem fought his way into the finals of the Barcelona Open by winning against Kyle Edmund, Daniel Evans, Yuichi Sugita, and Andy Murray. Three of these four players play for the same flag and Thiem won against each of them. Thiem is not exactly a champion of the current Davis Cup format–he has opted out of playing for Austria several times and has a rather poor record of 2-3 when he does compete–but in Barcelona he has, at least, shown that he can beat several players from the same country over a short amount of time. And that’s what Davis Cup is about, right?

In this post my goal is to put this statistical hiccup into some context. It is not the first time the Austrian defeated three players of the same nationality at one event: In 2016 at Buenos Aires Thiem already beat three players from Spain. However, given that Spanish players appear much more frequently in draws than Britons do, I will take a closer look.

Since 1990, there have only been three tournaments where a single player faced three players from Great Britain. And only one of these players who faced three Britons won each encounter. The following table shows the three tournaments and each of the matches where a player from Great Britain was faced by the same player. Wally Masur is the only player since 1990 who defeated three players from Great Britain in a single tournament. Thiem remains the only player who achieved this in a tournament outside of the island.

Tournament     Round Winner        Loser           Score
'93 Manchester R32   Wally Masur   Ross Matheson   6-4 6-4
'93 Manchester R16   Wally Masur   Chris Wilkinson 6-3 6-7(4) 6-3
'93 Manchester QF    Wally Masur   Jeremy Bates    6-4 6-3

'97 Nottingham R32   Karol Kucera  Martin Lee      6-1 6-1
'97 Nottingham SF    Karol Kucera  Tim Henman      6-4 2-6 6-4
'97 Nottingham F     Greg Rusedski Karol Kucera    6-4 7-5

'01 Nottingham R32   Martin Lee    Lee Childs      6-4 5-7 6-0
'01 Nottingham R16   Martin Lee    Arvind Parmar   6-4 6-3
'01 Nottingham QF    Greg Rusedski Martin Lee      6-3 6-2

Obviously, there are not many chances to face three Britons in a single tournament. And when one of those opponents is likely to be Andy Murray, a player’s chances of beating all three are even slimmer.

Let’s broaden the perspective a bit and take a look at how often a player defeated three (or more) players from the same country without looking only at Great Britain. The following table displays the results of this analysis. The first column contains the country, the second column (3W) shows how often a player defeated three players of this country, the third column (3WL) shows how often a player defeated two players of this country and then lost to a player of the same country, and so on.

Country  3W  3WL  4W  4WL  5W  5WL
USA      119 179  19  30   1   4
ESP      98  157  17  18   3   2
FRA      28  45   5   2    1   0
ARG      22  26   5   3    0   0
GER      15  18   1   1    0   0
AUS      13  9    0   0    0   0
SWE      9   16   1   0    0   0
CZE      4   5    0   0    0   0
NED      4   4    0   0    0   0
RUS      4   3    0   0    0   0
ITA      2   3    1   0    0   0
BRA      1   3    1   0    0   0
GBR      1   2    0   0    0   0
CHI      1   1    0   0    0   0
SUI      1   1    0   0    0   0

As we could have imagined, USA, ESP, and FRA come out on top here, simply, because for years they have had the highest density of players in the rankings. These are also the only countries of which a player was faced five times at a single tournament. Facing a player of the same country six or more times never happened according to the data at hand. The following table shows the most recent occasions of the entries printed in bold in the above table (5W).

Tournament    Round Winner        Loser             Score
'91 Charlotte R32   Jaime Yzaga   Chris Garner      7-6 6-3
'91 Charlotte R16   Jaime Yzaga   Jimmy Brown       6-4 6-4
'91 Charlotte QF    Jaime Yzaga   Michael Chang     7-6 6-1
'91 Charlotte SF    Jaime Yzaga   M. Washington     7-5 6-2
'91 Charlotte F     Jaime Yzaga   Jimmy Arias       6-3 7-5
'07 Lyon      R32   Sebastien Gr. Rodolphe Cadart   6-3 6-2
'07 Lyon      R16   Sebastien Gr. Fabrice Santoro   4-6 6-1 6-2
'07 Lyon      QF    Sebastien Gr. Julien Benneteau  6-7 6-2 7-6
'07 Lyon      SF    Sebastien Gr. Jo Tsonga         6-1 6-2
'07 Lyon      F     Sebastien Gr. Marc Gicquel      7-6 6-4
'08 Valencia  R32   David Ferrer  Ivan Navarro      6-3 6-4
'08 Valencia  R16   David Ferrer  Pablo Andujar     6-3 6-4
'08 Valencia  QF    David Ferrer  Fernando Verdasco 6-3 1-6 7-5
'08 Valencia  SF    David Ferrer  Tommy Robredo     2-6 6-2 6-3
'08 Valencia  F     David Ferrer  Nicolas Almagro   4-6 6-2 7-6

Finally, we take a look at the big four. Did they ever eliminate three or more players from the same country in a single tournament? Yes, they did. In 2014 Roger Federer beat three Czech players in Dubai. In 2005, 2008, and 2013 he beat three German players in Halle. In 2009 Andy Murray beat three Spanish players in Valencia. In 2007 Novak Djokovic beat three Spanish players in Estoril. In 2013 Rafael Nadal beat three Argentinian players both in Acapulco and Sao Paolo. In 2015 he even beat four Argentinian players in Buenos Aires. And there are many other examples where Rafa beat three of his countrymen at the same tournament.

We can see that this happens fairly often, specifically for countries where the tournament is organized, because more players of this country appear in the draw due to wild cards and qualifications. If we exclude these cases, Federer’s streak in Dubai stands out, as does Thiem’s streak in Barcelona.

Peter Wetz is a computer scientist interested in racket sports and data analytics based in Vienna, Austria.

Podcast Episode 6: Djokovic Therapy, More WTA Chaos, and Fivers in Roehampton

In the Episode 6 of the Tennis Abstract Podcast, Carl Bialik and I discuss Novak Djokovic’s new coaching situation, consider the prospects of last week’s title winners (Marin Cilic and Alexander Zverev among them), and continue to watch Maria Sharapova in her return to tour. We also lament Wimbledon’s decision to charge admission for qualies and rejoice in an American or two who can play on clay.

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Albert Ramos’s Record-Setting Doubles Futility

Last week, we learned that Albert Ramos is not very good at doubles. In Barcelona, he lost his first-round doubles match, running his losing streak to 21 straight and his career tour-level record to an astonishing 14-79.

Ramos hasn’t won a doubles match since Marrakech last year, so he has fallen off the doubles ranking list entirely. Elo isn’t so kind: Of the 268 players with at least one tour-level doubles match since 2014, Ramos ranks dead last, with an Elo rating of 1260, 130 points behind the second worst, Paul-Henri Mathieu, and 240 points below the default rating of 1500 given to a player when he first arrives on tour. If two players with Ramos’s rating were to play an elite team like Kontinen/Peers, Elo would give the Ramos team little more than a 2% chance of winning.

It turns out that the Barcelona loss was a notable one, setting the mark for the longest tour-level doubles losing streak since 2000. Here is the list:

PLAYER               LOSSES     YEARS  
Albert Ramos             21   2016-17*  
Florent Serra            20   2008-10  
Lars Burgsmuller         18   2001-03  
Ryan Sweeting            17   2010-12  
Mikhail Kukushkin        17   2014-16  
Gael Monfils             16   2012-15  
Jack Waite               16   2001-02  
Mikhail Youzhny          16   2002-03  
Luke Jensen              15   2000-02  
Ratiwatana brothers      15   2008-09  
Taylor Dent              15   2001-04

* active streak

My database isn’t as complete before 2000, so I can’t confidently say whether there were longer streaks earlier in ATP history.

Among active players, Ramos’s run of futility stands far above the pack. There are 14 players with active streaks of 8 or more tour-level losses, though as you’ll see, I’m defining “active” quite broadly:

PLAYER                STREAK  START  
Albert Ramos              21   2016  
Lukas Lacko               13   2012  
James Ward                11   2010  
Marinko Matosevic         11   2014  
Jimmy Wang                11   2006  
Zhe Li                    11   2010  
Omar Awadhy               10   2002  
Jose Rubin Statham        10   2006  
Mikhail Youzhny           10   2015  
Paul Henri Mathieu         9   2016  
Juan Monaco                9   2015  
Lucas Pouille              8   2016  
Andre Begemann             8   2016  
Daniel Gimeno Traver       8   2015

Many of the players on this list are attempting comebacks from injury or trying to rebuild their rankings to enter more ATP events, so few of them are likely to threaten Ramos’s mark. If he continues on tour, Mathieu may have the best chance: He has racked up five different losing streaks of 8 or more matches, including a 12-loss stretch between 2002 and 2005.

One of the things that makes Ramos’s streak so remarkable is that he has continued to enter doubles draws so frequently, playing both singles and doubles in 20 of his 31 events. Some of his peers have had poor doubles seasons, but few of them have kept trying so assiduously. Here are the 15 players with the worst doubles winning percentages in the last 52 weeks, minimum 10 matches:

PLAYER                   MATCHES  WINS  WIN PERC  
Albert Ramos                  20     0      0.0%  
Jiri Vesely                   10     1     10.0%  
Alexander Bury                13     2     15.4%  
Taylor Fritz                  11     2     18.2%  
Gilles Simon                  11     2     18.2%  
Benoit Paire                  16     3     18.8%  
Inigo Cervantes Huegun        10     2     20.0%  
Lucas Pouille                 15     3     20.0%  
Hans Podlipnik Castillo       13     3     23.1%  
Paolo Lorenzi                 33     8     24.2%  
Marcos Baghdatis              12     3     25.0%  
Adrian Mannarino              15     4     26.7%  
Andreas Seppi                 15     4     26.7%  
Joao Sousa                    30     8     26.7%  
Neal Skupski                  17     5     29.4%

Paolo Lorenzi might be a bit better than his position on this list makes him look: Over the last year, he has partnered Ramos four times, more than any other player.

Then again, Lorenzi has struggled with plenty of doubles partners. Here are the least successful doubles players since 2000, minimum 50 matches:

Albert Ramos             93    14     15.1%  
Robby Ginepri            97    21     21.6%  
Gilles Simon            151    33     21.9%  
Gael Monfils             92    21     22.8%  
Adrian Mannarino         58    14     24.1%  
Benoit Paire             93    23     24.7%  
Paul Henri Mathieu      105    26     24.8%  
Jack Waite               68    17     25.0%  
Florent Serra            72    18     25.0%  
Santiago Giraldo         99    27     27.3%  
Aleksandar Kitinov       88    24     27.3%  
Marinko Matosevic        61    17     27.9%  
Bernard Tomic            63    18     28.6%  
Younes El Aynaoui        56    16     28.6%  
Paolo Lorenzi           104    30     28.8%

Ramos, once again, is in a league of his own. Beyond him and Robby Ginepri, the list is dominated by a surprising number of Frenchmen, including Florent Serra, who outranks several of his countrymen, but appeared earlier with the 20-match losing streak that Ramos finally overtook.

Ironically, since Ramos’s losing streak has coincided with career-best success on the singles circuit, he will find it easier than ever to enter doubles draws. With the press that comes with the streak, however, potential partners may finally think twice before signing up with the worst tour-level doubles player of their generation.

Podcast Episode 5: Sharapova’s Back, Rafa’s the King, and Dropshots Are Cool

In the Episode 5 of the Tennis Abstract Podcast, Carl Bialik and I talk Sharapova, Grand Slam wild cards, Laura Siegemund, drop shot tactics, Nadal’s second Decima, and a couple of interesting doubles storylines.

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Why Maria Sharapova Should Get a French Open Wild Card

Maria Sharapova has returned from a 15-month doping suspension and hardly missed a step, advancing to the semifinals of her first tournament back, in the WTA Premier event in Stuttgart. While the draw has done her some favors–Ekaterina Makarova knocked out Agnieszka Radwanska, and Anett Kontaveit ousted Garbine Muguruza, Sharapova has shown she’s ready to compete at the highest level, winning about 57% of points against three credible opponents.

Many players have publicly stated that Sharapova doesn’t deserve to get wild cards, often because WCs are a sort of bonus, and a player who broke the rules doesn’t deserve any kind of handout. We’re likely to hear a lot more about it, as we won’t learn her status for the French Open for another two weeks.

However, wild cards are at the discretion of each individual tournament, and barring new regulations for players returning from doping bans, tournaments have their own incentives. Events often choose wild cards from a marketing perspective, granting main draw spots to former stars, young prospects, or local favorites.

Tournaments don’t have an explicit contract with their fans, but if they did, it would have to begin with an obligation to put the highest-quality product on the court. Most of the time, the ATP and WTA ranking and entry systems accomplish this, guaranteeing main draw places to the highest-ranked players. Occasionally, though, the ranking system fails and massively underrates the quality of a player.

Sharapova, obviously, is such a case. Unranked this week, and ranked #262 next week if she loses today to Kristina Mladenovic, she is already performing at the level of a top-20 player. My research suggests she may very soon be the best active player in women’s tennis, even if it takes many months for her official ranking to catch up.

Wild cards are the only mechanism tournaments are given to correct for the limitations of the ranking system. If the French Open (or any other event) wants to improve the quality of their draw, it should give Sharapova a wild card. If I am right that tournaments owe it to the fans to put on court the highest-level competition they possibly can, there are few opportunities so clear-cut as this one to improve the quality of a draw with a single player’s entry.

I can hear the objections already. First, as so many have claimed, Sharapova doesn’t “deserve” this kind of benefit. Yet by definition, wild cards are for players who don’t deserve a main draw entry. If they deserved one, their ranking (or “special” or “protected” ranking, if returning from injury) would guarantee them one. We use the words “deserve” and “earn” rather vaguely in this context, perhaps saying that a former great in his final year deserves a wild card based on his past contributions to tennis, or that a player has earned the free entry because she won a play-off of some sort.

It’s certainly true that some wild cards are more earned than others, but ultimately it’s beside the point. Even if it offends our sense of fairness, the players who most deserve a place in a draw are those who will make it more competitive. Last year, the French Federation gave wild cards to the likes of Alize Lim and Tessah Andrianjafitrimo, who lost in the first round to Qiang Wang without winning a single game. The eight wild cards won a total of three matches–one of them against another wild card. Except by virtue of being French, most of these wild cards didn’t do much to earn their places, and they had almost no impact on the tournament itself.

Beyond the claim that Sharapova, having broken the rules, doesn’t deserve a handout, there is a more extreme position, that her 15-month suspension wasn’t a sufficiently severe punishment. We can group that with another potential objection, that the French Open can’t be seen to endorse a doper. This is one of the many unfortunate side-effects of a weak central authority in tennis. By this argument, every tournament with the option of granting Sharapova an entry is required to re-litigate her doping ban. Even if we sidestep some of the controversial aspects of her ban and stipulate that she knowingly did something very bad, this seems nonsensical.

The whole point of having a central authority for doping enforcement is so that tournaments needn’t all police the players themselves. By issuing a 15-month ban, the ITF essentially spoke for all affiliated tournaments, saying that after 15 months (and exactly one day, as it turned out), Sharapova’s penalty would be paid and she would, in a sense, be rehabilitated. Giving a rehabilitated player a wild card is in no way an endorsement of her behavior, any more than giving a job to an ex-convict is an endorsement of the criminal act that put him in jail.

As a fan–even when I wish Sharapova wouldn’t win so many matches against my favorites–I want to see the best possible level of tennis every week. Now that her suspension is complete, every week that Sharapova wants to compete but can’t enter a top-level event is a missed opportunity for the sport. As great as the French Open is, it would be better with Sharapova than without her.

Diego Schwartzman’s Return Game Is Even Better Than I Thought

Diego Schwartzman is one of the most unusual players on the ATP tour. Even shorter than David Ferrer, his serve will never be a weapon, so the only way he can compete is by neutralizing everyone else’s offerings and winning baseline battles. Up to No. 34 in this week’s official rankings and No. 35 on the Elo list, he’s proven he can do that against some very good players.

Using the ATP stats leaderboard at Tennis Abstract, we can get a quick sense of how his return game compares with the elites. At tour level in the last 52 weeks (through Monte Carlo), he ranks third with 42.3% return points won, behind only Andy Murray and Novak Djokovic. He is particularly effective against second serves, winning 56.6% of those, better than anyone else on tour. He has broken in 31.8% of his return games, another third-place showing, this time behind Murray and Rafael Nadal.

Yet the leaderboard warns us to tread carefully. In the last year, Murray’s opponents have been far superior to Schwartzman’s, with a median rank of 24 and a mean rank of 41.5. The Argentine’s opponents have rated at 45.5 and 54.8, respectively. Murray, Djokovic, and Nadal are far better all-around players than Schwartzman, so they regularly reach later rounds, where the quality of competition goes way up.

Competition quality is one of the knottiest aspects of tennis analytics, and it is far from being solved. If we want to compare Murray to Djokovic, competition quality isn’t such a big factor. One or the other might get lucky over a span of months, but in the long run, the two best players on tour will face roughly equivalent levels of competition. But when we expand our view to players like Schwartzman–or even a top-tenner such as Dominic Thiem–we can no longer assume that opponent quality will even out. To use a term from other sports, the ATP has a very unbalanced schedule, and the schedule is always more challenging for the best players.

Correcting for competition quality is also key to understanding how any particular player evolves over time. If a player’s results improve, he’ll usually start facing more challenging competition, as Schwartzman is doing this spring in his first shot at the full slate of clay-court Masters events. If his return numbers decline, is he actually playing worse, or is he simply competing at his past level against tougher opponents?

Adjusting for competition

To properly compare players, we need to identify similarities in their schedules. Any pair of tour regulars have played many of the same opponents, even if they’ve never played each other. For instance, since the beginning of last season, Murray and Djokovic have faced 18 of the same players–some more than once. Further down the ranking list, players tend to have fewer opponents in common, but as we’ll see, that’s an obstacle we can overcome.

Here’s how the adjustment works: For a pair of players, find all the opponents both men have faced on the same surface. For example, both Murray and Djokovic have played David Goffin on clay in the last 16 months. Murray won 53.7% of clay return points against the Belgian, while Djokovic won only 42.1%, meaning that Djokovic returned about 22% worse than Murray did. We repeat the process for every surface-player combination, weight the results so that longer matches (or larger numbers of matches) count more heavily, and find the average.

When we do that for the top two men, we find that Djokovic has returned 2.3% better. (That’s a percentage, not percentage points. A great returner wins about 40% of return points, and a 2.3% improvement on that is roughly 41%.) Our finding suggests that Murray has faced somewhat weaker-serving competition: Since the beginning of 2016, he has won 42.9% of return points, compared to Djokovic’s 43.3%–a smaller gap than the competition-adjusted one.

It takes more work to reliably compare someone like Schwartzman to the elites, since their schedules overlap so much less. So before adjusting Diego’s return numbers, we’ll take several intermediate steps. Let’s start with the world No. 3 Stanislas Wawrinka. We follow the above process twice: Once for Wawrinka and Murray, then again for Stan and Novak. Run the numbers, and we find that Wawrinka’s return game is 22.5% weaker than Murray’s and 24.3% weaker than Djokovic’s. Wawrinka’s rates relative to the other two players correspond very well with what we already found, suggesting that Djokovic is a little better than his rival. Weighting the two numbers by sample size–which, in this case, is almost identical–we slightly adjust those two comparisons and conclude that Wawrinka’s return game is 22.4% worse than Murray’s.

Generating competition-adjusted numbers for each subsequent player follows the same pattern. For No. 4 Federer, we run the algorithm three times, one for each of the players ranked above him, then we aggregate the results. For No. 34 Schwartzman, we go through the process 33 times. Thanks to the magic of computers, it takes only a few seconds to adjust 16 months worth of return stats for the ATP top 50.

Below are the results for 2016-17. Players are ranked by “relative return points won” (REL RPW), where a rating of 1.0 is arbitrarily given to Murray, and a rating of 0.98 means that a player wins 2% fewer return points than Murray against equivalent opposition. The “EX RPW” column puts those numbers in a more familiar context: The top-ranked player’s rating is set equal to 43.0%–approximately the best RPW of any player in the last few seasons–and everyone else’s is adjusted accordingly.  The last two columns show each player’s actual rate of return points won and their rank among the ATP top 50:

1     Diego Schwartzman         1.04   43.0%   42.4%     4  
2     Novak Djokovic            1.02   42.1%   43.3%     1  
3     Andy Murray               1.00   41.2%   42.9%     2  
4     Rafael Nadal              0.98   40.3%   42.6%     3  
5     David Goffin              0.97   40.1%   41.3%     5  
6     Gilles Simon              0.96   39.6%   40.1%     9  
7     Kei Nishikori             0.95   39.3%   40.1%    10  
8     David Ferrer              0.95   39.1%   40.6%     7  
9     Roger Federer             0.94   38.7%   38.7%    15  
10    Gael Monfils              0.93   38.5%   39.8%    11  

11    Roberto Bautista Agut     0.93   38.3%   40.3%     8  
12    Ryan Harrison             0.92   37.9%   36.7%    33  
13    Richard Gasquet           0.92   37.9%   40.8%     6  
14    Daniel Evans              0.91   37.6%   36.9%    27  
15    Juan Martin Del Potro     0.91   37.5%   36.8%    32  
16    Benoit Paire              0.90   37.0%   38.1%    19  
17    Mischa Zverev             0.90   36.9%   36.9%    28  
18    Grigor Dimitrov           0.89   36.4%   38.2%    18  
19    Fabio Fognini             0.88   36.4%   39.7%    12  
20    Fernando Verdasco         0.88   36.4%   38.3%    16  

21    Joao Sousa                0.88   36.2%   38.3%    17  
22    Dominic Thiem             0.88   36.2%   38.1%    20  
23    Stani Wawrinka            0.88   36.1%   37.5%    22  
24    Alexander Zverev          0.88   36.0%   37.5%    23  
25    Albert Ramos              0.87   35.9%   38.9%    14  
26    Kyle Edmund               0.86   35.5%   36.1%    37  
27    Jack Sock                 0.86   35.5%   36.6%    34  
28    Viktor Troicki            0.86   35.4%   37.1%    26  
29    Marin Cilic               0.86   35.4%   37.3%    25  
30    Pablo Carreno Busta       0.86   35.3%   39.4%    13  

31    Milos Raonic              0.86   35.2%   36.1%    38  
32    Pablo Cuevas              0.85   35.1%   36.9%    29  
33    Tomas Berdych             0.85   35.1%   36.9%    30  
34    Borna Coric               0.85   34.9%   36.1%    39  
35    Nick Kyrgios              0.85   34.9%   35.7%    41  
36    Philipp Kohlschreiber     0.84   34.7%   37.9%    21  
37    Jo Wilfried Tsonga        0.84   34.6%   36.2%    36  
38    Sam Querrey               0.83   34.3%   34.6%    44  
39    Lucas Pouille             0.82   33.9%   36.9%    31  
40    Feliciano Lopez           0.81   33.2%   35.2%    43  

41    Robin Haase               0.80   33.0%   36.1%    40  
42    Paolo Lorenzi             0.80   32.9%   37.5%    24  
43    Donald Young              0.78   32.2%   36.3%    35  
44    Bernard Tomic             0.78   32.1%   34.1%    45  
45    Nicolas Mahut             0.76   31.4%   35.4%    42  
46    Steve Johnson             0.75   31.0%   33.8%    46  
47    Florian Mayer             0.74   30.3%   33.5%    47  
48    John Isner                0.73   30.0%   29.8%    49  
49    Gilles Muller             0.72   29.8%   32.4%    48  
50    Ivo Karlovic              0.63   25.9%   26.4%    50

The big surprise: Schwartzman is number one! While the average ranking of his opponents was considerably lower than that of the elites, it appears that he has faced bigger-serving opponents than have Murray or Djokovic. The top five on this list–Schwartzman, Murray, Djokovic, Nadal, and Goffin–do not force any major re-evaluation of who we consider to be the game’s best returners, but the competition-adjusted metric does offer more evidence that Schwartzman really belongs there.

There is a similar predictability at the bottom of the list. The five players rated the worst by the competition-adjusted metric–Steve Johnson, Florian Mayer, John Isner, Gilles Muller, and Ivo Karlovic–are the same five who sit at the bottom of the actual RPW ranking, with only Isner and Muller swapping places. This degree of consistency at the top and bottom of the list is reassuring: The metric is correcting for something important, but it isn’t spitting out any truly crazy results.

There are, however, some surprises. Three players do very well when their return games are adjusted for competition: Ryan Harrison, Daniel Evans, and Juan Martin del Potro, all of whom jump from the bottom half to the top 15. In a sense, this is a surface adjustment for Harrison and Evans, both of whom have played almost exclusively on hard courts. Players win fewer return points on faster surfaces (and faster surfaces attract bigger-serving competitors, magnifying the effect), so when adjusted for competition, someone who plays only on hard courts will see his numbers improve. Del Potro, on the other hand, has been absolutely hammered by tough competition, so in his case the correction is giving him credit for the difficult opponents he has had to face.

Several clay court specialists find their return stats adjusted in the wrong direction. Last week’s finalist, Albert Ramos, falls from 14th to 25th, Pablo Carreno Busta drops from 13th to 30th, and Roberto Bautista Agut and Paolo Lorenzi see their numbers take a hit as well. This is the reverse of the effect that pushed Harrison and Evans up the list: Clay-court specialists spend more time on the dirt and they play against weaker-serving opponents, so their season averages make them look like better returners than they really are. It appears that these players are all particularly bad on hard courts: When I ran the algorithm with only clay-court results, Bautista Agut, Ramos, and Carreno Busta all appeared among the top 12 in competition-adjusted return points won. It’s their abysmal hard-court performances that pull down their longer-term numbers.

Beyond RPW

This algorithm–or something like it–has a great deal of potential beyond simply correcting return points won for tour-level competition quality. It could be used for any stat, and if competition-adjusted return rates were combined with corrected rates of service points won, it would generate a plausible overall player rating system.

Such a rating system would be more valuable if the algorithm were extended to players beyond the top 50, as well. Just as Schwartzman doesn’t yet have that many common opponents with the elites, Challenger-level stalwarts don’t have share many opponents with tour regulars. But there is enough overlap that, when combining the shared opponents of dozens of players, we might be able to get a better grip on how Challenger-level competition compares to that of the highest levels. Essentially, we can compare adjacent levels–the elites to the middle of the pack (say, ATP ranks 21 to 50), the middle of the pack to the next 50, and so on–to get a more comprehensive idea of how much players must improve to achieve certain goals.

Finally, adjusting serve and return stats so that we have a set of competition-neutral numbers for every player, for each season of his career, we will gain a clearer picture of which players are improving and by how much. Official rankings and Elo ratings tell us a lot, but they are sometimes fooled by lucky breaks, close wins, or inconsistent opposition. And they cannot isolate individual stats, which may be particularly useful for developmental purposes.

Adjusting for opposition quality is standard practice for analysts of many other sports, and it will help tennis analytics move forward as well. If nothing else, it has shown us that one extreme performance–Schwartzman’s return game–is much more than a fluke, and that service return greatness isn’t limited to the big four.