Should Andy Murray Skip the Tour Finals to Prepare for Davis Cup?

After advancing to the Davis Cup final, Andy Murray floated the idea that he might skip the World Tour Finals to prepare. The Belgian hosts are likely to choose clay for November’s Davis Cup tie (in part to make Murray less comfortable), and if Murray reached the final round in London the week before, he would have only four days off to recover and adjust to the different surface.

A lot of factors will go into Murray’s ultimate decision: how much importance he gives each event, how much he thinks fatigue will affect him, and how likely it is that the ATP would sanction him for skipping a required event. For today, I’ll have to ignore all of those and focus on the one most amenable to analysis: The effect of switching surfaces right before a Davis Cup tie.

Shifting from one surface to another immediately before Davis Cup is common. From 2009 to the present, there have been just over 2,000 World Group, Group 1, and Group 2 Davis Cup singles rubbers, and almost 450 of those involved at least one player who had played the previous week [1] on a different surface. It’s very rare that both players switched surfaces, so we have a sample of 432 matches in which one player changed surfaces from the previous week, and the other player either played or (presumably) prepared on the same surface.

At the simplest level of analysis, the switchers have been surprisingly effective. In those 432 matches between switchers and non-switchers, the switchers won 275, or 63.6% of the time. When we narrow the sample to the 130 times the switcher reached at least the round of 16 the week before Davis Cup (and, thus, had even less time to adjust), the results are surprisingly similar: 82 wins, or 63.1% in favor of the switchers.

Of course, there are all sorts of biases that could be working in favor of the switchers. The better the player, the less likely he can change his schedule to better prepare for Davis Cup, leaving him stuck on the “wrong” surface the week before a tie. And the better the player, the more likely he was a switcher in the smaller sample, one of those who reached the round of 16 the week before.

To evaluate the effect of switching, then, we must proceed with more subtlety. If switchers are more likely to be the favorites, we need to consider each player’s skill level and estimate how often switchers should have won. To do that, we can use JRank, my player rating system with surface-specific estimates for each competitor.

Immediately, we lose about 15% of our sample due to matches involving at least one player who didn’t have a rating at the time [2]. These are almost all Group 2 matches, so its doubtful that we lose very much. In the slightly smaller pool of 361 matches, the switcher won 62.0%, and when the switcher reached the round of 16 the previous week, he won 60.0%.

JRank confirms that the sample is strongly biased toward switchers. The player changing surfaces was favored in 69.8% of these contests. To take an extreme example, Murray went from hard courts at the 2013 US Open to clay courts in the World Group playoff against Croatia. Against Borna Coric, who hadn’t played the week before, Murray was a 99.1% favorite, and of course he won the match.

Once we calculate the probability that the switcher won each of the 361 matches, it turns out that the switchers “should have” won 227, or 62.8% of the time. That’s almost indistinguishable from the historical record, when the switchers won 224 matches. In the smaller sample of 120 matches when the switcher reached the round of 16 the previous week, switchers “should have” won 72 matches. As it happened, they won exactly 72.

In other words, it doesn’t appear to be a disadvantage to play Davis Cup matches on an unfamiliar surface. JRank-based predictions are primarily based on “regular” matches, so if switchers are performing at the level that JRank forecasts for them, they’re playing as well as they would at, say, the third round of a Slam, when the surface is familiar.

This isn’t a clear answer to Murray’s dilemma, of course. If he plays, say, Roger Federer and Novak Djokovic in back-to-back three-setters on Saturday and Sunday, then travels to a different venue, handles tons of press, and practices with a different set of coaches and fellow players before a big match the following Friday, he faces more of a challenge than your typical surface-switcher in our dataset.

However, there’s little evidence that surface-switching alone is a good reason to skip the Tour Finals. If history is any guide, Murray will play very well on the Belgian clay–just as well as he would at the same venue in the middle of the clay season.

Continue reading Should Andy Murray Skip the Tour Finals to Prepare for Davis Cup?

Unlikely Davis Cup Finalists and an Early Forecast for Ghent

Among nations that have reached Davis Cup finals, neither Great Britain or Belgium quite fits the mold.

The fortunes of the UK team depend almost entirely on Andy Murray. If you have to choose one player, you couldn’t do much better, but it’s hardly a strategy with lots of room for error. While the Belgian team is a bit more balanced, it doesn’t boast the sort of superstar singles player that most successful nations can send into battle.

Thanks to injury and apathy, the Brits and the Belgians haven’t defeated the level of competition usually required of Davis Cup finalists. Belgium hasn’t had to face any singles player better than Leonardo Mayer, and the only top-ten singles player to show up against Britain was Gilles Simon.

Measured by season-best singles rankings, these are two of the weakest Davis Cup finalists in the modern era [1]. The last time a finalist didn’t have two top-50 singles players was 1987, when the Indian team snuck past the Australians in the semifinals, only to be trounced by a powerhouse Swedish side in the final. This year, neither side has two top-50 players [2].

It’s even worse for the Belgians: David Goffin, their best singles player, has never topped 14th in the rankings. Only three times since 2000 has a nation reached the final without a top-ten player, and to find a side that won the Davis Cup without a top-tenner, we must go back to 1996, when the French team, headed by Arnaud Boetsch and Cedric Pioline, claimed the Cup.

Even when a nation reaches the final without a top-ten singles player, they typically have another singles player in the same range. Yet Belgium’s Steve Darcis has only now crept back into the top 60.

Despite a widespread belief that you can throw logic out the window in the riot that is Davis Cup, the better players still tend to win. Here are Elo-rating-based predictions for the four probable rubbers on clay:

  • Murray d. Darcis (94.3%)
  • Goffin d. GBR-2 (90.1%)
  • Murray d. Goffin (86.7%)
  • Darcis d. GBR-2 (78.1%)

Predicting the outcome of any doubles matches–let alone best-of-five-setters with players yet to be determined, probably including one very good but low-ranked player in Andy Murray–is beyond me. But based on the Murray brothers’ performance against Australia and the Belgians’ lack of a true doubles specialist, the edge has to go to Britain–let’s say 65%.

If we accept these individual probabilities, Great Britain has a 65.2% chance of winning the Davis Cup. That doesn’t take into account home court advantage, which will probably be a factor and favor the Belgians [3].

It’s a huge opportunity for the Brits, but it’s still quite a chance for Belgium, which hasn’t been this close to the Davis Cup for a century.  After all, the Cup is inscribed with country names, not judgments about that nation’s easy path to the final.

Continue reading Unlikely Davis Cup Finalists and an Early Forecast for Ghent

Berdych, Djokovic, and Stars in Davis Cup

Tennis fans–especially the more old-fashioned among us–tend to agree on some things that players should always do.  Among them: revere Wimbledon, admit to a net touch, and play Davis Cup.

The top singles players on the two sides of last weekend’s tie between Serbia and the Czech Republic are good examples of what fans like to see.  Tomas Berdych has played 12 of 14 Davis Cup ties while a member of the top ten, and in that time, the Czech team has never lost a tie because he didn’t show up.  Novak Djokovic hasn’t been quite as reliable, playing singles in 13 of 18 ties since breaking into the top ten, though of the five he didn’t play, Serbia lost only one.

However, plenty of tennis megastars have been even more consistent cogs on their national teams.  In the years when Goran Ivanisevic was in the top ten, his Croatian team played ten ties, and Goran was there for all 10.  Since 1991, three other players have played at least ten ties while missing only one: Yevgeny Kafelnikov, Lleyton Hewitt, and Michael Stich.

Aside from Berdych and Djokovic, today’s top players are not so reliable.  Roger Federer has participated in 14 of 24 ties since he became a top-tenner, and the Swiss side has lost eight of the ten ties he’s missed.  Andy Murray has offered his services for only 5 of 12 as a top ten player, and the Brits have lost four of their seven Murray-less weekend.

Even less of a Davis Cup stalwart than Murray, however, is Rafael Nadal.  Thanks to a combination of injury, fatigue, and a frequent lack of necessity, Rafa has played singles in only 10 of 25 ties since breaking into the top ten.

The table below compares all players who, since 1991, have been in the top ten while their countries played at least ten Davis Cup ties.  It shows their record when participating (“In W-L”), their team’s success rate when they sat out (“Out W-L”), the percentage of ties in which they took part (“In%”), and the percentage of ties in which either they played or their team won anyway (“AllGood%”).

(I only count someone as participating if he contested at least one singles match.  In a few cases–such as Serbia’s defeat last year of Sweden, in which Djokovic only played doubles–that blurs the line between wins with and without the player.)

Player              In W-L  Out W-L     In%  AllGood%  
Goran Ivanisevic       5-5      0-0  100.0%    100.0%  
Yevgeny Kafelnikov    13-6      0-1   95.0%     95.0%  
Lleyton Hewitt        10-3      0-1   92.9%     92.9%  
Michael Stich          8-2      0-1   90.9%     90.9%  
Andy Roddick          15-5      0-3   87.0%     87.0%  
David Nalbandian      11-2      0-2   86.7%     86.7%  
Tomas Berdych          9-3      2-0   85.7%    100.0%  
Carlos Moya            8-4      1-1   85.7%     92.9%  
Stefan Edberg          8-3      2-0   84.6%    100.0%  
Marcelo Rios           5-3      2-0   80.0%    100.0%  
Novak Djokovic        10-3      4-1   72.2%     94.4%  
Nikolay Davydenko      8-3      4-1   68.8%     93.8%  
David Ferrer           7-2      3-2   64.3%     85.7%  
Marat Safin            7-0      2-3   58.3%     75.0%  
Roger Federer         10-4      2-8   58.3%     66.7%  
Boris Becker           5-2      5-3   46.7%     80.0%  
Andy Murray            3-2      3-4   41.7%     66.7%  
Jim Courier            6-0      6-3   40.0%     80.0%  
Rafael Nadal           9-1     10-5   40.0%     80.0%  
J M Del Potro          1-3      6-1   36.4%     90.9%  
Pete Sampras           8-3     16-6   33.3%     81.8%  
Andre Agassi           7-2    14-10   27.3%     69.7%  
Michael Chang          2-1     13-3   15.8%     84.2% 

Doubles Wins and Davis Cup Results

Today, Tomas Berdych added another chapter to his outstanding Davis Cup doubles career, partnering Radek Stepanek to give his Czech Republic a 2-1 lead in this weekend’s Davis Cup final.

The absence of Janko Tipsarevic meant that the doubles rubber was particularly crucial.  While Novak Djokovic will probably defeat Berdych tomorrow, Stepanek is equally likely to dismiss Dusan Lajovic, giving the Czechs a second consecutive Davis Cup title.

Since the Saturday doubles match is so often a pivotal juncture in a Davis Cup tie, I was curious whether the doubles match was particularly predictive of the end result.  If you’re a believer in momentum, it would seem possible.

However, if a side is to take a 2-1 lead, it’s better to win two singles matches and lose the doubles than to drop one of the singles matches.  Or, to put it another, probably more accurate, way: It’s best to have a squad that dominates the singles.  (Stunning insight, I know.)

There have been 435 World Group ties (including playoffs) since 1981 in which the outcome was undecided after the doubles match.  In 296 of those, the two sides split the singles.  In the other 139, one side swept the first-day singles and the opposing team won the doubles.

Of the first group of 296, the side that won the doubles won 80.4% of ties.  That pales in comparison to the singles-sweeping sample. Of those 139 ties, the side that won both singles and lost the doubles proved triumphant 93.5% of the time.

This shouldn’t be too surprising.  Momentum or no momentum, the third day of a Davis Cup tie is nothing but singles matches.  When the outcome is to be decided by two singles rubbers, would you rather have two great singles players or a pair of momentum-swaying doubles players?

Fortunately for the Czechs, 80% is still awfully good, and it probably understates the likelihood that Stepanek will beat Lajovic tomorrow.   Nice as it would have been to sweep opening-day singles, it helps to have a backup plan when Djokovic is playing for the other side.

In Search of Davis Cup Heroes

Come up big for one important weekend, and you can earn a reputation as a Davis Cup hero that lasts a lifetime.  We tend to remember big stories and crucial moments more than career-long trends, so images of Radek Stepanek holding last year’s trophy loom larger in memory than his mediocre-sounding 12-11 record in live singles rubbers.

This isn’t to say that Stepanek isn’t a Davis Cup hero.  Some matches are more important than others, and even 12-11 can be impressive when you consider that four of his 11 losses came against top-ten players.  And that’s to say nothing about doubles.

To find out who really performs under the scrutiny of Davis Cup crowds, we need to go deeper.  We must determine how many matches a player like Stepanek should’ve won, then compare his actual mark.  When we do that with two decades of Davis Cup results, we find some unsung stalwarts and some overrated superstars.  The international competition isn’t the endless source of upsets that pundits like to insist it is, but some players do provide us with more upsets than others.

Here’s how it works.  For every live Davis Cup rubber, we take each player’s ranking and estimate the likelihood that each player would win the match.  In the case of today’s match between Stepanek and Novak Djokovic, we might estimate that the Serbian has a 95% chance of winning.  Then we compare the results.  If Novak wins, he’ll outperform expectations by five percentage points (100% instead of 95%), while the Czech underperforms by the same amount (0% instead of 5%).

Do that for every match, tally the results for every player, and things start to get interesting.

Among active and recently-active players, there’s an unusual twosome near the top of the rankings: Juan Martin del Potro and David Nalbandian. (Delpo partisans will be glad to know that he just edges out his older compatriot.)  Del Potro has won 11 of 15 live rubbers, though based on his competition, we would only have expected him to win eight.  Four of those wins were over higher-ranked players.  Nalbandian is a stunning 23-6 in live singles rubbers (including 6-4 against higher-ranked players), while we would have expected him to win between 17 and 18.

Both Argentines have outperformed their rankings, winning between 32% (Nalbandian) and 36% (Delpo) more matches than we would expect.  Of those with at least ten live rubbers under their belts, the only active player to better those marks is Frank Dancevic.  The Canadian has won three live rubbers despite never facing a lower-ranked player in any of his ten matches.  3-7 may not seem awe-inspiring, but the numbers suggest he should have won only one match, with an outside shot at a second.  He has more than doubled that.

(I’m setting the standard here at 10 live rubbers. But it would be foolish to ignore Amir Weintraub, who has been historically great in his seven live rubbers.  Like Dancevic, he has never faced a lower-ranked player in Davis Cup, yet he has amassed a 4-3 record, despite an expectation of between one and two wins.)

How about the familiar faces this weekend?  Stepanek has racked up about 13% more Davis Cup singles wins than expected, while Tomas Berdych is slightly positive, at +4%.  Djokovic and his almost-teammate Janko Tipsarevic are a bit below expectations.  This isn’t really a knock on Novak, though.  When you’ve spent so many years close to top, expectations are very high.  Also, his two high-profile Davis Cup retirements–against Delpo in 2011 and against Nikolay Davydenko in 2008–count against him.  Take out those two matches, and his mark swings to a +4%, equal to Berdych.

In any event, no modest over- or underperformance is likely to swing the singles matches in this weekend’s tie.  Even a sluggish Djokovic would probably whip a hero-mode Stepanek.  Neither Novak or Berdych has displayed enough of a Davis Cup-specific tendency to alter the outcome of their match.  And Tipsarevic’s replacement, Dusan Lajovic, would need to channel his inner Dancevic to have any impact at all.

If hero-mode Stepanek is to alter the course of this tie, it will probably happen in the doubles rubber.  Unfortunately for Radek, I don’t have the numbers to disprove a strong suspicion that the most outrageous overperformance in Davis Cup this year belongs to Ilija Bozoljac, one of the men who will be standing across the net from him for–we can only hope–five sets tomorrow.

After the jump, I’ve included +/- numbers like those cited above for many top-ten and otherwise interesting players.

Continue reading In Search of Davis Cup Heroes

Are There More Five-Setters in Davis Cup?

There’s no denying that Davis Cup gives us some of the most dramatic moments on the men’s tennis calendar.  It’s easy, then, to fall prey to some mistaken conventional wisdom, such as the canard that upsets are much more common in the international competition.

(In fact, upsets are only more common if Amir Weintraub is playing.)

Even if the favorites usually win, what about hard-fought matches?  Is it possible that any given Davis Cup match is more likely to go the distance than a Grand Slam match?

It sounds good, but no, the frequency of five-setters (and even four-setters, for that matter) is steady regardless of context.  Since 2003, 18.7% of Grand Slam matches have gone five sets, while just 17.5% of best-of-five Davis Cup rubbers have gone that far.

There are differences among levels of Davis Cup, as we might expect.  19.9% of best-of-five World Group rubbers go five, and 20.3% of World Group playoff rubbers go five.  But neither of these numbers stands out compared to some subsets of Slam matches.  19.6% of second-round matches at majors reach a fifth set, while 20.3% of fourth-rounders and 20.6% of quarterfinal matches do so.

Here is the complete breakdown by set length:

Davis Cup       2496   56.6%   25.9%   17.5%  
Grand Slams     5453   51.2%   30.1%   18.7%  

DAVIS CUP                                              
World Group      473   51.0%   29.2%   19.9%  
WG Playoffs      261   52.9%   26.8%   20.3%  
Group 1          688   54.9%   27.5%   17.6%  
Group 2         1074   61.0%   23.3%   15.7%  

GRAND SLAMS                                            
F                 44   40.9%   40.9%   18.2%  
SF                88   51.1%   29.5%   19.3%  
QF               173   52.0%   27.2%   20.8%  
R16              340   49.4%   30.3%   20.3%  
R32              686   51.5%   30.2%   18.4%  
R64             1368   49.0%   31.4%   19.6%  
R128            2754   52.5%   29.4%   18.1%

There are good reasons why we believe Davis Cup five-setters to be so much more common.  At the World Group level, there are never many matches going on, so if two players reach a fifth set–especially if it is the day’s second rubber, after other ties have finished play for the day–it is global tennis news.  It’s easy to recall Dudi Sela‘s five-set battles against Vasek Pospisil and Kei Nishikori in the 2011 and 2012 World Group playoffs, but how many of us paid a moment’s attention to Sela’s four-hour clash with Andrey Kuznetsov in the first round of this year’s US Open?

Further, the Davis Cup atmosphere leaves the impression that every match is gripping, even when it isn’t.  Janko Tipsarevic beat Pospisil in straight sets yesterday, but thanks to the pair of tiebreaks and the electricity of the Serbian home crowd, we’ll remember that match differently than a typical 7-6 6-2 7-6 victory at a Grand Slam.

Fortunately, fan enjoyment isn’t measured in sets.  There is plenty to get excited about–especially the weekend of World Group playoffs–even if upsets and five-set matches aren’t any more frequent than usual.

Team GB and the Rarity of Davis Cup Comebacks

Last weekend, the British Davis Cup squad pulled off a major upset, defeating the Russian team 3-2.  Even more impressively, all three of their wins came while facing elimination.  The Russians won the two singles matches on the first day before Britain claimed the doubles rubber and both of the reverse singles rubbers on the final day.

It was the first time since 1930 that Britain won a Davis Cup tie from a 2-0 deficit.  It’s also one of the very few times in the modern era that any country has won a tie after failing to post a point on the first day.

Since the formation of the current structure in 1981, there have been 1310 completed ties in the World Group and Group 1, including playoffs.  In 802 of those (61.2%), one team has raced out to a 2-0 lead by sweeping the first-day singles matches.

Of those 802 ties, Britain’s comeback was only the 19th in this 33-year span, and the first since Canada surged to victory against Ecuador in 2011.  Playing the tie at home doesn’t seem to help the underdogs: Only eight of those 19 comebacks came at home.

Many Davis Cup ties, especially at the Group 1 level, are quite lopsided, so clinching the tie with the doubles match is quite common.  In fact, that’s what has happened in nearly half of all ties at the World Group and Group 1 levels since 1981 (577, or 44.0%).  So once a squad is down 2-0, the odds are massively stacked against them.  Here are the historical outcomes for teams that sweep day one:

Clinched in…              
3rd rubber    577  71.9%  
4th rubber    159  19.8%  
5th rubber     47   5.9%  

Won           783  97.6%  
Lost           19   2.4%

Here are the 19 odds-busting ties:

Year                     Home  Surface  Winner  
2013  G1 R2: GBR vs RUS  GBR   Hard     GBR     
2011  G1 R2: ECU vs CAN  ECU   Clay     CAN     
2010  G1 PO: KOR vs PHI  KOR   Hard     PHI     
2010  WG PO: IND vs BRA  IND   Hard     IND     
1998  WG R1: SVK vs SWE  SVK   Clay     SWE     
1997  G1 QF: PHI vs INA  PHI   Clay     INA     
1997  WG R1: ROU vs NED  ROU   Hard     NED     
1996  WG SF: FRA vs ITA  FRA   Carpet   FRA     
1996  G1 PO: TPE vs INA  TPE   Hard     INA     
1995  WG SF: RUS vs GER  RUS   Clay     RUS     
1995  G1 PO: PER vs BAH  PER   Clay     BAH     
1995  WG R1: DEN vs SWE  DEN   Carpet   SWE     
1994  WG SF: SWE vs USA  SWE   Carpet   SWE     
1992  WG R1: CAN vs SWE  CAN   Carpet   SWE     
1990  G1 QF: IRL vs ROU  IRL   Carpet   ROU     
1989  G1 SF: PER vs BRA  PER   Clay     PER     
1988  G1 F: INA vs KOR   INA   Clay     INA     
1988  WG PO: SUI vs MEX  SUI   Carpet   MEX     
1988  G1 QF: PHI vs JPN  PHI   Clay     PHI

It can be done, even in the late rounds of the World Group.  But generally, it’s a good idea to start off the weekend by winning a singles match or two.