# 2019 French Open: Glicko Preview

### ABOUT THE AUTHOR: MARTIN INGRAM – DATA SCIENTIST

Martin is passionate about good code and gaining insights from data with a particular interest in sports analytics. He completed a Bachelor Of Arts, Natural Sciences (Physical) at Cambridge before completing his Masters of Science, Computing Science.

In this preview, I use Glicko, a ratings system originally developed by Harvard Professor Mark Glickman, to rank the French Open players. Glicko is a generalisation of the Elo rating system which considers not just a player’s mean skill, but also the uncertainty about that skill.

This allows Glicko to deal more naturally with player absences than Elo: if a player is out of the competition for long periods, Glicko becomes more uncertain and makes larger adjustments to their rating when they return. If you would like to know more about Glicko, you can have a look at the original paper or a less technical write-up here.

Player abilities can vary greatly across surfaces. To take players’ clay court preferences into account, I fit a version of Glicko which weighs their results on clay courts more heavily.

### What do the Glicko rating differences mean?

Before diving into the numbers, I would like to briefly mention what the differences in Glicko skill mean in terms of win probability.

The exact formula is given in the Glicko paper, equation 16. It’s a little involved, but the graph above shows the basic functional relationship. The x-axis is the difference in player vs opponent skill; for example, if the player is rated 1600 and the opponent 1500, that translates to an opponent Glicko edge of -100, since their skill is 100 points lower.

The graph shows that the win probability is then around 60% (the exact value is 63.2%). Note that this graph assumes that the uncertainty is 80 for both players, but it does not vary greatly for different values.

### Men's

The table below shows the top 8 favourites according to clay Glicko.

Player Mean Skill Skill uncertainty
2 Novak Djokovic 2040 73
3 Roger Federer 1966 79
4 Dominic Thiem 1952 68
5 Juan Martin Del Potro 1883 86
6 Stefanos Tsitsipas 1880 70
7 Kei Nishikori 1831 71
8 Alexander Zverev 1810 71

The top favourite is Rafael Nadal, as he has been for so many years on clay. Even though he has had a worse clay season than he is used to – losing in the semi-finals of Monte Carlo (to Fognini), Barcelona (to Thiem) and Madrid (to Tsitsipas), he most recently won Rome, defeating Tsitsipas and Djokovic en route and dropping only one set, suggesting he may be peaking in time for Paris. At 2184 Glicko points, he has a 144-point edge over Novak Djokovic, making him a 68.7% favourite in a head to head match.

Novak Djokovic comes in second, at 2040 points. After a stellar start to the year with a victory at the Australian Open, he played poorly at Indian Wells and Miami, losing in the second and third rounds, respectively. His recent performance on clay has been strong, however: he won Madrid and reached the final in Rome. He is also one of only two players to have beaten Nadal at the French Open (the other is Robin Söderling, now retired).

After Djokovic and Nadal, two players follow with a gap of around 80 points: Roger Federer (1966) and Dominic Thiem (1952). Both are within 14 points of each other, making a match between them a very close affair according to Glicko – Federer would be favoured, but only just (51.9%). They both would have a roughly 23% chance of beating Nadal, and 40% against Djokovic.

Federer is playing on clay this year for the first time since 2016, and last played the French Open in 2015. He lost to Thiem in Madrid in an extremely close match where he held match points and had to withdraw from his match against Tsitsipas in Rome, casting some doubt on his fitness, especially since his clay schedule was very light to begin with.

Thiem has had ups and downs this clay season, losing in the second round of Monte Carlo and the first round of Rome, but reaching the semi-finals in Madrid and winning in Barcelona, where he defeated Nadal on the way to the final. When he is playing well, he is very tough to beat on clay, and he is definitely a player to look out for this year.

Juan Martin del Potro (1883) comes in at number 5, which is perhaps somewhat surprising. Del Potro has struggled with injuries since the end of last year and has only played three tournaments this year: Delray beach (lost to McDonald), Madrid (lost to Djere in the first round), and Rome (lost to Djokovic). In that last match, he had two match points, suggesting that he may be finding some form. If he is physically fit again, he may live up to his high rating.

Only three points separated Del Potro from Stefanos Tsitsipas (1880), who has had some big successes on clay this year, winning Estoril and reaching the finals of Madrid, beating Nadal in the semi-finals. In Rome, Nadal got his revenge, beating Tsitsipas in the semi-finals. Given that Tsitsipas is only 20 years old, he is a player worth paying attention to. However, with a gap of over 300 points to Nadal, his probability of beating him is still just 16% according to Glicko, suggesting that he would not be expected to repeat his Madrid victory.

Nishikori (1831) is ranked 7th by Glicko. Nishikori is always a player to be reckoned with, but his clay court season has not been stellar. He lost in the first round of Monte Carlo, then reached the semi-finals of Barcelona (lost to Medvedev), the second round of Madrid (lost to Wawrinka) and the quarter finals of Rome (lost to Schwartzman).

Finally, Alexander Zverev rounds out the top 8, with 1810 points. After an excellent clay court season in 2018 leading up to the French Open, his 2019 clay season has been disappointing, his best result being a quarter final in Madrid (lost to Tsitsipas). He is still playing in Geneva at the time of writing, so perhaps he can still recover his form.

### Winners and losers compared to last year

Among the 32 players ranked highest by Glicko, 22-year-old Christian Garin has made the biggest gains, adding an astonishing +389 points to his rating. Matteo Berrettini comes in second, with +261, followed by Daniil Medvedev (+238), Stefanos Tsitsipas (+194), Guido Pella (+137) and Novak Djokovic (+105).

The player with the biggest losses over the last year is Alexander Zverev (-147). David Goffin (-123), Grigor Dimitrov (-98), Nick Kyrgios (-70) and Marin Cilic (-62) are also rated worse than they were this time last year.

### Women's

Player Mean skill Skill uncertainty
1 Kiki Bertens 1915 67
2 Simona Halep 1908 76
3 Petra Kvitova 1882 73
4 Ashleigh Barty 1837 81
5 Karolina Pliskova 1830 73
6 Naomi Osaka 1803 75
7 Serena Williams 1799 102
8 Elina Svitolina 1788 84

The table above shows the top 8 favourites on the women’s side.

Two players are ranked closely together at the top: Kiki Bertens (1915) and defending champion Simona Halep (1908). Bertens had an impressive run in Madrid, beating Kvitova and Halep, among others, on the way to the title.

She also reached the semi-finals in Rome (lost to Konta) and Stuttgart (lost to Kvitova), suggesting that she is currently on good form. After withdrawing from Stuttgart with an injury, Halep played well in Madrid, reaching the final, but lost in the first round of Rome (to Vondrousova), where she seemed to struggle with a leg injury.

Petra Kvitova (1882) follows with just a small gap of around 30 points. Glicko gives her a 45% chance against Bertens, and 46% against Halep. She has had a fairly good clay season, winning Stuttgart (beating Bertens in the semi-finals) and reaching the quarters in Madrid (lost to Bertens) but had to retire in the second round of Rome against Sakkari. That last retirement casts some doubt on her prospects at the French Open.

Bertens, Halep and Kvitova are all ranked highly, and Ashleigh Barty comes in fourth with a slight gap (1837), which translates to a win probability of about 40% against Bertens. She has been rising rapidly in the rankings and had a fantastic tournament on the hard courts of Miami, beating Bertens, Kvitova and Pliskova on the way to the title.

Her clay court season has been more mixed, with a quarter final in Madrid (lost to Halep), a second-round loss in Rome (to Mladenovic) and she most recently had to withdraw from Strasbourg with an arm injury, making her form for the French Open questionable, too.

Karolina Pliskova is only 7 points away from Barty (1830). She finished the clay court season very strongly, winning Rome, which suggests she may be a player to look out for.

Reigning US Open and Australian Open champion Naomi Osaka is ranked 6th by Glicko. She has struggled since her Australian Open title run and most recently had to withdraw from her quarter final match against Bertens in Rome. If she can regain her form, she is certainly a title contender, but this is currently doubtful.

Three-time winner of the French Open, and 23-time Grand Slam champion Serena Williams, comes in 7th. Her uncertainty is by far the largest, at 102 points, suggesting that Glicko is very unsure of her rating.

Williams has only played four tournaments so far this year and was forced to retire in her last three matches. She has tended to find some form for the Grand Slams in the past however, reaching the finals at last year’s US Open, and losing a close match to Pliskova at the Australian Open, so it would probably be a mistake to count her out completely.

Finally, Elina Svitolina rounds out the top 8. Svitolina has had poor results since reaching the semi-finals of Indian Wells, losing in the first round of Miami, Madrid and Rome, which does not bode well for her prospects at the French Open.

### Winners and losers compared to last year

Among the players ranked in the top 32, Belinda Bencic (+224) has gained the most since last year. Vondrousova (+151), Bertens (+150), Putintseva (+143), Ashleigh Barty (+134), Jo Konta (+110) and Sofia Kenin (+100) have also improved their Glicko rating dramatically.

The biggest loser compared to last year is Elina Svitolina (-116). Caroline Garcia (-88), Elise Mertens (-87), Caroline Wozniacki (-80), Serena Williams (-67) and Sloane Stephens (-60) have all lost a significant number of points.

### Summary

Both the men’s and the women’s tournaments at this French Open promise to be intriguing. On the men’s side, Nadal has been looking more vulnerable than in previous years, though he is still the heavy favourite.

Djokovic is the second favourite, following with a slight gap, and Federer and Thiem are the next most likely. It will be fascinating to see whether Nadal and Djokovic can live up to their high ratings or whether a younger player like Thiem can have their breakthrough Grand Slam win.

On the women’s side, players are more closely ranked together, but there are three players who have a slight edge over the field: Bertens, Halep and Kvitova. Among these, only Bertens has not struggled with injuries recently.

On the other hand, Kvitova and Halep have won Grand Slams before, while Bertens has not, which may help them somewhat. Finally, Karolina Pliskova may be worth looking out for, given her recent strong play in Rome.

### Betting Strategy

BACK: Rafael Nadal to win the French Open

BACK: Simona Halep to win the French Open

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