Nadal, ranked three, reached the final of the US Open each of the past two years, winning the title in 2010 to complete a career Grand Slam. But in 2011, Novak Djokovic beat him to win the title.
“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 tweeted.
Nadal was beaten by 100th-ranked Lukas Rosol in Wimbledon on June 28 and since then he has not played a match.
Shortly after that defeat, Nadal cancelled a scheduled charity match against Djokovic in Spain, citing tendon problems in his left knee.
The 26-year-old Nadal also pulled out of the London Olympics — he won the gold medal at Beijing in 2008, and was supposed to carry Spain’s flag in the opening ceremony this time.
US Open director David Brewer said in a statement issued Wednesday: “Rafa has informed us that he will not be ready to compete at the US Open this year and has withdrawn from the tournament.
“We hope to see him back on the court soon and look forward to his return to New York next year.”