The 30-year-old Swiss star wrote in a letter to the organizing committee in Shanghai that he needs "necessary time to rest and recuperate after a long summer."

　　"I have some nagging injuries that I need to address and I look forward to returning to the ATP World Tour as soon as possible," he added.

　　Federer played two Davis Cup singles matches and a doubles match in Australia last weekend, just days after losing to eventual champion Novak Djokovic in the U.S. Open semifinals in New York.

　　The 16-times grand slam winner apologized to his fans and said he looks forward to returning to Shanghai for the 2012 event.

　　"I have very fond memories of Shanghai so I will miss this amazing tournament and all my loyal Chinese fans, but I look forward to returning to China next fall," said Federer.