Roger Federer and Rafael Nadal have never met at the U.S. Open. A showdown in Queens this year between these two famous rivals — which could only happen in the final — would be mandatory viewing for tennis fans. But despite the history between these two stars, their rivalry is not the greatest in men’s tennis history. No, that claim belongs to Nadal and Novak Djokovic.

You might be laughing out loud at that. But the numbers speak for themselves. Since their first meeting in 2006, Djokovic and Nadal have gone mano a mano in 54 matches, according to the ATP Tour — the most between any two players in the Open era, which began in 1968. What’s more, their career series is remarkably close: Djokovic has won 28, while Nadal has won 26.

Every other significant rivalry in modern history is more lopsided, in addition to having fewer total matches. John McEnroe and Jimmy Connors played 34 times, with McEnroe holding a bigger edge than Djokovic does over Nadal. Likewise, Pete Sampras and Andre Agassi played 34 times, and Sampras won 20 to Agassi’s 14.

Djokovic versus Nadal is the greatest rivalry in men’s tennis The most frequently occurring men’s singles tennis matchups in the Open era, along with each player’s win total in the rivalry Player 1 Player 2 Name Wins Wins Name Novak Djokovic 28 – – 26 Rafael Nadal Novak Djokovic 26 – – 22 Roger Federer Rafael Nadal 24 – – 16 Roger Federer Ivan Lendl 21 – – 15 John McEnroe Novak Djokovic 25 – – 11 Andy Murray John McEnroe 20 – – 14 Jimmy Connors Ivan Lendl 22 – – 13 Jimmy Connors Boris Becker 25 – – 10 Stefan Edberg Pete Sampras 20 – – 14 Andre Agassi Rafael Nadal 26 – – 6 David Ferrer Source: ATP

When they first met at the French Open in 2006, Nadal and Djokovic had one major title between the two of them. Now, Nadal has 18 while Djokovic has 16 — and at ages 33 and 32, respectively, they could both reach or surpass Federer’s current major record of 20.

Federer and Nadal have played epic matches, including most famously when Nadal beat Federer in five sets at the 2008 Wimbledon final, finishing in the waning light at 9:15 p.m. local time. But Federer and Nadal have played 14 matches in majors versus 15 for Nadal and Djokovic. Federer vs. Djokovic is a remarkable rivalry, too, but they also have not played as many times overall (48). And unlike Djokovic and Federer or Federer and Nadal, Djokovic and Nadal have met in the final of all four Grand Slams. Djokovic is also one of only two men to beat Nadal at the French Open; he did so in the quarterfinals in 2015.

And Djokovic and Nadal’s rivalry is more competitive in the Slams, as well, with Nadal winning nine major matches to Djokovic’s six. By comparison, Nadal leads 10 to four against Federer at majors.

Even if you rate Nadal’s win over Federer in the famous 2008 Wimbledon match as the greatest men’s match of this era, Djokovic and Nadal have had some epic showdowns, too. The final of the 2012 Australian Open is right there among the greats. The sets were long with a lot of running, improbable winners and extra T-shirts. In the end, Djokovic prevailed in a five-hour, 53-minute slog. They both had difficulty standing during the trophy ceremony.

Other matches have been similarly captivating. In the semifinals of the French Open in 2013, Nadal beat Djokovic 9-7 in the fifth set — capping a clay-court marathon that lasted four hours and 37 minutes. At Wimbledon last year, also a semifinal, the match was played under the roof, even when they had to finish the match the next day. Nadal lost in the fifth set, 10-8.

Djokovic and Nadal may meet again soon; if it’s in this U.S. Open, a potential 55th match between the two — the event’s top seeds — would come in the final on Sept. 8. And if not, perhaps because of the shoulder injury Djokovic is nursing, there will likely be many more big matches between them in the future. They’re still in their primes, and they’re just too good to stay away from each other.