Nadal out of US Open
Concerns over Rafael Nadal's long-term fitness deepened when the Spaniard pulled out of the US Open with the knee injury that has sidelined him since Wimbledon.
- Related Content
The world number two, who completed his set of grand slams by winning in New York in 2010, was forced to miss the Olympics and the Masters Series events in Toronto and Cincinnati with the injury, and is still not ready to compete.
Nadal said in a statement: "I am very sad to announce that I am still not ready to play and have to withdraw from this year's US Open in NYC.
"I am sorry since I always found great crowds and great support, but I have to continue with my recuperation and preparation to be ready to play in the right conditions."
While the announcement will come as a big disappointment to the tournament and Nadal's many fans, it is not unexpected.
The 26-year-old has not played since his shock second-round defeat by Czech Lukas Rosol in the second round of Wimbledon in June.
Nadal subsequently pulled out of a scheduled exhibition against Novak Djokovic in Madrid citing knee problems and then announced he would not be able to defend his title at the Olympics, where he had been due to carry Spain's flag at the opening ceremony.
Nadal has been dogged by knee problems throughout his career, although he has stressed this injury is not related to his previous problems, and took a month off after the Australian Open this year to give his body a rest.
He has always found hard courts the most wearing on his joints and, when he pulled out of Toronto and Cincinnati, it became increasingly unlikely he would risk returning to the circuit at the year's final grand slam.
Nadal, who is now almost certain to lose his world number three ranking to Andy Murray, reached the final of the US Open last year for the second year in a row but lost in four sets to Djokovic.
The US Open begins at Flushing Meadows on August 27, with Roger Federer and Djokovic heading the men's rankings, while David Ferrer is likely to be elevated to fourth seed.
Federer was asked about Nadal ahead of this week's tournament in Cincinnati and he admitted his surprise at the length of the Spaniard's absence.
"I was going to write to him and check on him because I can't believe he's been out that long," said Federer.
"I thought the Olympics, okay, that's fine. That's a personal choice.
"I thought for sure we would see him in Toronto, but now he missed Toronto and Cincinnati. It's very surprising, because it was nothing that we heard of prior to the injury.
"He played so well on clay, and then actually seemed fine at Wimbledon. He had more time by losing earlier at Wimbledon. I'm sad for him."