FILE - This Aug. 30, 2011 file photo shows Rafael Nadal, of Spain, serving to Andrey Golubev, of Kazakhstan, during the first round of the U.S. Open tennis tournament in New York. The U.S. Open says that Nadal has withdrawn from the last Grand Slam tennis tournament of the year because of injury. (AP Photo/Charles Krupa, File)

FILE - This Sept. 12, 2011 file photo shows Rafael Nadal of Spain reacting during the championship match against Novak Djokovic of Serbia at the U.S. Open tennis tournament in New York. Nadal has withdrawn from the 2012 U.S. Open tournament. (AP Photo/Charles Krupa)

FILE - This Sept. 10, 2011 file photo shows fans watching Rafael Nadal of Spain play Andy Murray of Britain as the sun sets over the New York City skyline during a semifinal match at the U.S. Open tennis tournament in New York. The U.S. Open says that Nadal has withdrawn from the last Grand Slam tennis tournament of the year because of injury. (AP Photo/Charlie Riedel, File)

FILE -- In a Sept. 11, 2011 file photo Samantha Stosur of Australia poses with the championship trophy after beating Serena Williams at the U.S. Open tennis tournament in New York. In many ways, that 6-2, 6-3 victory over Serena Williams in the U.S. Open final seems more distant than just last year. (AP Photo/Matt Slocum, file)