NEW YORK – Rafael Nadal’s Grand Slam count will stay stuck at 11 for now, sidetracked by another knee problem.

The third-ranked Spaniard withdrew from the U.S. Open on Wednesday. Tendinitis has kept him out of action since his stunning loss at Wimbledon in late June.

The injury already forced him out of the London Olympics, where he was supposed to defend his title and carry Spain’s flag in the opening ceremony.

“I am very sad to announce that I am not ready to play the US Open in NY. Thanks to my fans for their support and specially, the new yorkers,” Nadal wrote on his Twitter account.

Nadal is still only 26, but the withdrawals raise questions about the future of a player who has had recurring knee problems in the past.

His 11 Grand Slam titles include a record seven on the red clay of the French Open, yet his hard-charging, hard-hitting style of play takes a toll on his body, particularly his knees.

Roger Federer, in contrast, has played in every Grand Slam tournament since the start of 2000, a streak of 51 in a row.

In 2009, Nadal missed Wimbledon because of aching knees shortly after falling in the Round of 16 at the French Open — the only time in eight appearances he hasn’t won at Roland Garros. He was just the second men’s champion in 35 years to decline to defend his title at the All England Club.

But Nadal eventually came back stronger than ever from that layoff. After failing to reach the final at the 2009 U.S. Open and 2010 Australian Open, he won the French to start a run of three straight major titles, capped by completing the career Grand Slam at Flushing Meadows.

Nadal’s absence immediately leaves a trio of heavy favorites at the last Grand Slam event of the year: defending champion Novak Djokovic; five-time U.S. Open winner and currently top-ranked Federer; and 2008 U.S. Open runner-up Andy Murray, who won the gold medal in singles at the London Games by beating Federer in the final.

“It’s obviously a shame. I like Rafa a lot as a friend,” Murray said after winning at the Western & Southern Open outside Cincinnati.

“Yeah, I’m disappointed for him. But I think for tennis and also a major competition, it’s a huge benefit when you have the top players playing.”