Rafael Nadal dropped out of the Western & Southern Open on Thursday because of a knee problem that also forced him to miss the Olympics.
Nadal pulled out of the London Olympics because of a sore left knee, missing the chance to be Spain's flag bearer in the opening ceremony.
He won the French Open for a record seventh time at the start of the season, but has been bothered by a problem with the tendon in the knee for weeks. He lost in the second round at Wimbledon and hasn't played since then, dropping out of the Olympics and the Rogers Cup this week.
The Masters event in suburban Mason begins on Sunday. Nadal will be the only man ranked in the Top 10 who's not in the tournament.
"Hi all, another message to announce something that definitely doesn't make me happy but unfortunately I won't be competing at the tournament in Cincinnati next week," Nadal posted on his Facebook page Thursday. "I am still not ready to play. I have many fans in Cincy and unforgettable moments such as 2008. I am continuing with my recup (recovery) and practice. Thanks."
Nadal will be the only man currently ranked in the ATP's top 10 to miss the tournament. Gold medalist Serena Williams leads the women's field that includes nine of the top 10 WTA players.
Nadal has been one of the most popular players at the Cincinnati tournament, drawing large crowds to his matches.
"We're certainly disappointed that Rafa won't be able to play in Cincinnati this year," tournament director Vince Cicero said. "He's one of the great competitors in the sport and he will be sorely missed."