Italian translation at settesei.it
This is a guest post by Peter Wetz.
Novak Djokovic’s loss against Benoit Paire in his first match at this year’s Miami Masters caused a lot of head scratching. Not only did Benoit equalize his head to head against Novak–next to Hyeon Chung he is now the only active player with a balanced record against Novak; four active players hold positive records–but this was also the Serbian’s third consecutive loss.
Novak immediately made some changes, announcing the end of his partnership with his coach Andre Agassi and part-time coach Radek Stepanek after having worked with them just a few months.
A losing streak of this length by such a dominant player must be rare, and it prompted me to look for similar instances among the big four. The following table shows all three (or more) match losing streaks of the big four after they cracked the top ten in reverse chronological order. The last column shows the Elo-based probability (Prob) of having such a streak. This is simply the product of the probabilities of losing the matches that made up the streak.
Player Start End Length Prob Djokovic 2018-01-15 -* 3 0.002% (0.027%**) Murray 2011-01-17 03-23 4 0.02% Murray 2010-03-11 04-11 3 0.63% Nadal 2009-11-08 11-22 4 1.89% Djokovic 2007-10-15 11-12 5 0.07% Federer 2002-07-08 08-19 4 0.66% * Streak still active ** Probability when adjusting Elo ratings due to absence from the tour
The table shows that since August 2002 Roger Federer never lost more than two matches in a row. Even his four match losing streak is the second most likely due to the strong competition he had to face. In November 2009 Rafael Nadal lost four matches in a row, but with a probability far higher than the other streaks. The reason is that three of the four matches occurred at the World Tour Finals, increasing the likelihood of a loss.
A number that stands out is the probability of Novak’s current streak: 0.002%. However, this number is based on traditional Elo ratings which do not take into account player absence, for instance, due to injury. Before this season Novak took a six month break suffering from a shoulder injury.
As has already been discussed, there are ways to adjust Elo ratings for players coming back on the tour. In the case of Maria Sharapova, who stayed absent for 15 months, a 200 point drop in her first five matches after the break was more in line with her level of play than simply assuming that she remained as competitive as before. For this analysis I used a drop of 150 rating points for Novak, which results in a more realistic streak probability of 0.027%, still the second lowest in the list.
This brings us to Andy Murray‘s losing streak of 2011, which most of us probably have already forgotten. After losing the Australian Open final to Novak, Andy lost against Marcos Baghdatis (#20) in Rotterdam, Donald Young (#143) in Indian Wells, and Alex Bogomolov (#118) in Miami. This looks very similar to Novak’s current situation, but Murray bounced back to achieve a 50-9 record for the remainder of the season. It remains to be seen whether Djokovic can do the same.
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Peter Wetz is a computer scientist interested in racket sports and data analytics based in Vienna, Austria.