MASON, Ohio -- Rafael Nadal dropped out of the Western & Southern Open on Sunday night, scuttling a reunion of the "Big Four."
Nadal withdrew a few hours after he won his fifth title of the year in Toronto, beating Stefanos Tsitsipas 6-2, 7-6 (4). Instead of playing more grueling matches in Cincinnati, he'll take a week to get some rest and get ready for the U.S. Open.
"No other reason than personally taking care of my body and trying to keep as healthy as I feel now," Nadal said in a statement.
And so the "Big Four" reunion will have to wait for at least a few more weeks. Nadal, Roger Federer, Novak Djokovic and Andy Murray haven't played in the same tournament in more than a year. With Nadal's withdrawal, Federer becomes the top player in the men's bracket in Cincinnati.
Of the three left, Murray has the most to gain in Cincinnati.
Murray missed 11 months following hip surgery and tried to return for Wimbledon, but withdrew when he wasn't satisfied with his workouts. Cincinnati will be his fourth tournament in his comeback. He reached the quarterfinals at Washington two weeks ago, his best result.
Murray will play Lucas Pouille in the opening round on Monday afternoon. Bulgaria's Grigor Dimitrov is the defending champion. He didn't drop a set and lost his serve only once while getting his first Masters title.
Federer has a record seven titles in Cincinnati, which is one of his favorite tournaments with its low-key setting. He and No. 1-ranked Nadal have been locked in a season-long, back-and-forth atop the rankings, exchanging the top spot six times in the past six months. Nadal is guaranteed to take the top ranking into the U.S. Open.
While Federer has had great success in Cincinnati -- winning 41 of his past 45 matches -- Djokovic has never won a Western & Southern title, the only ATP Masters 1000 championship to elude him. He has reached the finals five times and lost every time, acknowledging that the pressure has played a part.
Djokovic is trying once again to become the first to win all nine ATP Masters events.
In the women's bracket, Serena Williams faces Daria Gavrilova on Monday night, her first match since she suffered the most lopsided defeat of her career. The 23-time Grand Slam champion lost 6-1, 6-0 to Johanna Konta in San Jose, then withdrew from the Rogers Cup in Montreal.
Williams had a baby in September and developed blood clots. She was the runner-up at Wimbledon last month, her fourth tournament since she returned to the tour. When she withdrew from the Rogers Cup, the 36-year-old Williams said she has been struggling with postpartum emotions.
"Not only was I accepting some tough personal stuff, but I just was in a funk," Williams said in an Instagram post . "Mostly, I felt like I was not a good mom."
Stephens is preparing to defend her surprising U.S. Open title last year. She was the runner-up in the French Open, but lost in the opening round at Wimbledon for the second straight year. The loss to Halep on Sunday left her 0-8 against No. 1-ranked players.