FILE - In this Friday May 4, 2012 file photo Spain's Rafael Nadal gestures after a press conference in Madrid. Nadal will take as much rest as his body needs before returning to tennis. The third-ranked Spaniard said said Friday Aug. 17, 2012 "I have to listen (to the doctors) and will be patient, and I will come back when my knee is well." (AP Photo/Paul White, File)
**FILE** Rafael Nadal reacts Sept. 12, 2011, during the championship match against Novak Djokovic at the U.S. Open tennis tournament in New York. (Associated Press)
**FILE** Rafael Nadal returns a shot to Ivan Ljubicic during their match on March 20, 2010, at the BNP Paribas Open tennis tournament in Indian Wells, Calif. (Associated Press)
Rafael Nadal of Spain Lukas reacts after losing a point to Rosol of the Czech Republic during a second round men's singles match at the All England Lawn Tennis Championships at Wimbledon, England, Thursday, June 28, 2012. (AP Photo/Anja Niedringhaus)
Rafael Nadal of Spain and Novak Djokovic of Serbia pose for photographers ahead of the final match at the French Open tennis tournament in Roland Garros stadium in Paris on Monday, June 11, 2012. Rain suspended the final, which was won by Nadal, making it the first French Open not to end on Sunday since 1973. (AP Photo/Bernat Armangue)
Spain's Rafael Nadal returns the ball to Serbia's Novak Djokovic during their men's final match in the French Open tennis tournament at the Roland Garros Stadium in Paris on Monday, June 11, 2012. (AP Photo/Michel Euler)
Novak Djokovic of Serbia returns in the men's final match against Rafael Nadal of Spain at the French Open tennis tournament in Roland Garros Stadium in Paris on Sunday, June 10, 2012. The match was suspended until Monday because of rain. (AP Photo/David Vincent)
Rafael Nadal celebrates winning his quarter final match against Nicolas Almagro at the French Open atRoland Garros stadium in Paris on Wednesday June 6, 2012. Nadal won in three sets: 7-6, 6-2, 6-3. (AP Photo/Bernat Armangue)
Spain's Rafael Nadal returns the ball to Serbia's Novak Djokovic during their final match at the Italian Open tennis tournament, in Rome, Monday, May 21, 2012. (AP Photo/Riccardo De Luca)
Rafael Nadal, who ended a run of seven losses to Novak Djokovic in title matches, has won 42 straight matches in the Monte Carlo Masters. He won his first title since last year's French Open. (Associated Press)
Rafael Nadal withdrew from his semifinal match against Andy Murray due to a knee injury, at the Sony Ericsson tennis tournament, Friday, March 30, 2012, in Key Biscayne, Fla. (AP Photo/Lynne Sladky)
Novak Djokovic of Serbia kisses the trophy during the award ceremony after defeating Rafael Nadal of Spain in the men's singles final at the Australian Open tennis championship, in Melbourne, Australia, early Monday, Jan. 30, 2012. (AP Photo/Rick Rycroft)
Novak Djokovic of Serbia serves to Rafael Nadal of Spain during the men's singles final at the Australian Open tennis championship in Melbourne, Australia, on Sunday, Jan. 29, 2012. (AP Photo/John Donegan)