French Open Simulation Predicts Rafael Nadal Will Win All-Time Record 21st Slam

by David Arkow

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The French Open begins this week with tennis’ Big 3 approaching a critical point in the Slam race. Roger Federer and Rafael Nadal are tied with 20 Grand Slam titles each; Novak Djokovic trails not far behind with 18. And for the first time since Federer surpassed Pete Sampras’s record in 2009 (14 Slams), it is conceivable that the men’s tennis world might be ready to crown a new GOAT by the end of this season—if not this fortnight. The pressure is likely on Nadal. This is his best Slam, and Djokovic is the favorite at Wimbledon and the U.S. Open. It seems plausible that at the end of this season, we will have a new Grand Slam leader among the Big 3. However, don’t count out the rest of the field, as this year we’ve seen the rise of younger competition in Daniil Medvedev, 25; Dominic Thiem, 27; Stefanos Tsistipas, 22; and Alexander Zverev, 24. So who are the biggest favorites going to the French Open? Who are the dark horses? And which players are overrated? To attempt to answer those questions, we simulated the tournament to find estimated probabilities for every single player in the draw to not only reach any given round but also to win it all.


Trying to predict outcomes with probabilities is common in sports. But it is much easier to do in a single game between two teams or even your standard 16-team playoff bracket than it is for a Grand Slam tennis tournament with a draw size of 128. This is because a lot of the probabilities are interdependent and can change meaningfully with each result, particularly unexpected ones. For example, if Nadal were to lose in an earlier round in the draw (as unlikely as that might be), Djokovic’s probability of winning the French would go drastically up since he would no longer have to play Nadal. 

Nevertheless, we can still try to predict the outcome of the French Open through a simulation. For my simulation, I used Tennis Abstract’s Elo ratings, which can be adjusted for different surfaces. For example, Nadal ranks behind Djokovic in overall Elo, but on clay the two flip-flop. Now, with the actual draw, we can simulate the tournament thousands of times using Elo ratings to see the different potential outcomes. This will ultimately give us a probability of each player making a certain round or even winning. For instance, if Djokovic wins the simulation 3,000 out of 10,000 times, he has an approximately 30% chance of winning. While there is seeding in tennis (No. 1-No. 32) the draw is more random than in other professional playoffs, which rely purely on seeding. In a Grand Slam, a No. 1 seed could play a No. 17 seed or a No. 32 seed in the third round. This creates possibilities for many interesting matchups throughout the tournament, with potential upsets besetting star players. 

The Big 3

Rafael Nadal: It’s no surprise that the King of Clay, winner of 13 French Open titles, is the favorite to win again at Roland Garros. He currently has the highest clay Elo rating (2,100) but by one of the smaller margins of his career. Not only is he tightly tailed by Djokovic, but young guns like Tsitsipas, Zverev and Thiem are not far behind. Nevertheless, Novak will be No. 1 on Rafa’s radar as they are both on the same half of the draw. If he were to play Djokovic, he would still be favored, with Elo giving him a 57% chance of winning: Nadal is 18-7 on clay and 7-1 at the French against the Serbian star. Djokovic has only beaten him once at Roland Garros, in the 2015 quarterfinals. Nadal has also had a pretty solid run up to Roland Garros, winning the Barcelona 500 and the Italian Open. Nadal is the slight favorite to win at 22%, and while fans might find this too low for the Spaniard who has only lost twice at Roland Garros, these are still pretty good odds for a 128-player field. If it was assumed that Nadal was constantly an 80% favorite in each match (which is pretty significant), his odds of winning the tournament would be about 21% (.8^7). While Nadal has the highest odds to win and lead the Big 3 in Slams after the tournament, it will be one of his toughest roads to do so. 

Roger Federer: Despite playing only a single tournament in 2020 (Australian Open, reaching the semifinal), Federer still ranks No. 8 in the world and is seeded No. 8 at Roland Garros (the ATP changed its ranking system from a rolling 12-month system to a 22-month system due to COVID-19). Federer, 39, missed all of 2020 with a knee injury and has only played two tournaments in 2021, suffering second- and first-round exits. He’s also playing on his weakest surface—his career winning percentage on clay is 76.1%, compared to 83.3% on hard and 87.4% on grass. Of his 103 career titles, Federer has only won 10 on clay and has not won a clay court tournament since 2015 (Istanbul). While tennis fans will continue to hope that Federer can win another Slam, the French is definitely the least likely of the four to add to his total. He would have to go through archrival Djokovic in the quarters (of which Elo gives him only a 21% chance). Federer even acknowledges that he has little-to-no chance of winning the French, and the simulation gives him a mere probability of 0.7%. Just making the second weekend should be considered a success for him (37% chance), especially coming back from injury, which could set the tone for a successful Wimbledon, historically his best tournament. 

Novak Djokovic: It is pretty clear that Djokovic is the best overall player in men’s tennis right now. But he might not be the best clay court player. Still, with their clay court Elos as close as they’ve ever been, a Djokovic-Nadal semifinal would be an excellent matchup. It also happens to be statistically the most common semifinal matchup, with a 23% probability of occurring. Djokovic is hoping to redeem himself from last year’s final, which he lost 6-0, 6-2, 7-5 to the King of Clay. Interestingly, if we exclude Nadal from the draw and replace him with an average player, Djokovic’s tournament win probability jumps from 19% to 25%, so he will be hoping for Rafa to be upset. Most fans, however, will be wishing for a Nadal vs. Djokovic rematch, which will be pivotal in the career Grand Slam race. He’s had the most recent clay court success winning his hometown tournament in Belgrade just this past weekend despite not facing tough competition (average ATP ranking of his opponents was 181). Djoker’s competition will be much tougher this week but he still has good odds to win it all.

Next Favorites and Dark Horses

Stefanos Tsitsipas: Tsitsipas actually has the third highest clay Elo rating, giving him an 11% probability of winning. He’s had the third best clay-court season (after Nadal and Djokovic), winning the Monte Carlo Masters 1000, winning the Lyon Open, reaching the finals at Barcelona, and losing in a tight three-setter to Djokovic at the Italian Open. His clay Elo has risen from 1,976 (fifth best) to 2,025 (third best) since the start of the clay-court season. Not only has Tsitsipas been good on clay this year, it’s historically been his best surface. He made a run to last year’s French Open semis and owns a career 72% winning percentage on the dirt, compared to 64% on hard and 53% on grass. Despite being the No. 5 seed, he is the favorite in his bottom quarter of the draw, as he would be expected to beat No. 2 seed Medvedev (73% chance) if the two were to face off in the quarters.

Alexander Zverev: Tennis fans remember the days when Zverev was touted as the phenom most likely to dispatch the Big 3. While he has been consistent, finishing in the Top 10 since he broke out in winning both the ATP Masters in Rome and Canada in 2017, Zverev has only reached one major Grand Slam final—the 2020 U.S. Open, which he came devastatingly close to winning over Thiem. The two are in the same quarter of the draw, and this potential match could be one of the most exciting of the tournament, rated a near 50-50 toss-up by Elo. Zverev has had a solid clay-court season, winning Madrid by beating Nadal in the quarters. Clay is also Zverev’s strongest surface, winning 70% of his matches over his career. Despite being lower than Tsitsipas in Elo rating (2017 vs. 2026), Zverev has a higher probability of coming out of the bottom half (27% vs. 21%) and Big 3-absent part of the draw. Zverev has a much easier path, with his first two matches guaranteed to be against qualifiers. Look for him to capitalize on his easier draw and make a deep run in Paris.

Jannik Sinner: Sinner is probably the hottest young name on the tour right now. The Italian, only 19 years old, is already No. 19 in the world and has the 11th highest clay Elo rating (1882). After last year’s improbable march to the quarters at the French, defeating No. 11 seed David Goffin and the sixth-seeded Zverev, look for Sinner to make a run in his first Grand Slam as a seeded player. He’s also an exciting player to watch, often being compared to Roger Federer for his calm court demeanor and offensive flat forehand. He is slated for a potential Round of 16 matchup with the King of Clay, who ousted him in straight sets at last year’s quarterfinals. While still an underdog (23% chance to defeat Rafa), he’s improved his game and his odds in the past year.


Daniil Medvedev: While Medvedev is currently the No. 2 player in the world, his probability of advancing far at Roland Garros is not nearly as high. Medvedev had to pull out of Monte Carlo after testing positive for COVID-19, so he’s only had two clay court warm-up tournaments, both of which were early round exits. Believe it or not, Medvedev has never won a single match at the French Open, despite playing the tournament four times. He is 10-18 in his career on clay, so even though he has the third highest overall Elo at the moment, he ranks 14th in clay Elo (1850) giving him only a 1.2% chance to win the French. This makes a lot of sense given his flat baseline game and big, flat serve, both of which are more neutralized on clay. Although he is the highest seed in his half of the draw, he’s eighth likeliest to emerge from that half, with only a 4% chance. Don’t be surprised if he’s the earliest upset among the top players; he has only a 37% chance to make the second weekend. 

Americans: It might not be so much that American tennis players are overrated but that there has been a drought of American success at Grand Slams, especially the French. The Americans have not had a French Open winner let alone a finalist in this century (Andre Agassi was the last, in 1999). This makes sense given that clay is usually the weakest and least played-on surface for Americans. This year’s French looks especially grim, with less than a 1% chance that any American wins. There are two all-American first-round matchups set to “cannibalize” each other: John Isner against former doubles partner Sam Querrey, and Steve Johnson vs. Frances Tiafoe. The best shots for the Americans are Taylor Fritz, Isner and Reilly Opelka, who are the No. 30-32 seeds. All are big servers, and clay is their weakest surface. If you’re looking to watch an American man, tune in to the opening rounds before they are all gone. However, there is a lot more optimism for their female counterparts with young players like Coco Gauff or Madison Keys, as American women combined have about 10 times the chance of winning the French as the American men (4% vs. 0.4%).

The French Open always makes for an exciting tournament, with lots of intriguing matchups, long rallies and big upsets. This year’s field sees familiar favorites like Nadal and Djokovic, the long-awaited return of Federer, and the potential emergence of new stars like Thiem, Tsitsipas, Zverev or Sinner. This Slam will prove to be vital in the Big 3 race and is guaranteed to be one for the history books.

David Arkow ’24 is an economics major and member of the Harvard Varsity Men’s Tennis Team. He also serves on the board of HSAC. If you have any questions about this article, you can reach out to him Also check out his preview and predictions for the women’s side of the draw.

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