Nadal suffered a three-set defeat to Croatia's Borna Coric on his return to action in Cincinnati
Russia's Daniil Medvedev is guaranteed to head to the US Open as world number one after Rafael Nadal was beaten on his comeback from injury at the Cincinnati Masters on Wednesday.
Returning for the first time since pulling out of his Wimbledon semifinal in July with an abdominal injury, Nadal suffered a three-set defeat to Croatia's Borna Coric in their second-round meeting, losing 7-6, 4-6, 6-3 after two hours, 51 minutes of action.
It was a strong display from the 25-year-old Coric, who is finding his way back to form after returning from shoulder surgery earlier this year.
The result has direct implications for Medvedev as world number three Nadal was the only man who could usurp him at the top of the ATP charts after Cincinnati.
For that to happen, the 22-time Grand Slam champion would have needed to win the tournament, while Medvedev would have needed to bow out before the quarterfinal stage.
Medvedev is already into the third round in Cincinnati, and faces Canada's Denis Shapovalov on Thursday for spot in the last eight.
Even if he loses, Medvedev is guaranteed to arrive at the US Open at the end of August as world number one, with the Russian looking to defend the Grand Slam title he won in New York last year.
Medvedev is currently enjoying a 13th week in total as the ATP leader - extending his record for a Russian male professional.
Nadal, 36, was philosophical after his defeat to former world number 12 Coric, who now boasts a 3-2 head-to-head career record against the Spanish great.
"Obviously I didn't play my best match," Nadal said in his post-match press conference.
"Historically this tournament has been difficult for me. So coming back from a tough period of time, [it is] something that's easy to accept and easy to say congrats to Borna, that he played better."
Nadal revealed that the lingering injury concerns which had forced him to withdraw from the Canadian Open last week meant that he had only played two practice sets before the Cincinnati Masters.
"I need to practice. I need to return better. I need days [on the court], and that's the truth," Nadal said.
Even though he fell at the first hurdle in Cincinnati, few would write off Nadal's chances at Flushing Meadows - not least as he has defied injury concerns on the way to winning two of the three Grand Slams on offer already this year.
Nadal is a four-time US Open champion, last winning the title in 2019, when he beat Medvedev in a five-set epic.
"I need to move forward and just start to think about the energy that the crowd gives me in New York," Nadal said, as quoted by the ATP website.
"I know it's a very special place for me, and I enjoy it. [I've had] unforgettable moments there, and I'm going to try my very best every single day to be ready for that."
Coric, meanwhile, moves into the third round in Cincinnati, where he will meet Spain's Roberto Bautista Agut.