Rafael Nadal, of Spain, hits autographed balls to fans after beating Richard Gasquet, of France, during the semifinals of the 2013 U.S. Open tennis tournament, Saturday, Sept. 7, 2013, in New York. (AP Photo/Charles Krupa)
Rafael Nadal, from Spain, reacts after winning the first set against John Isner during the finals match at the Western & Southern Open tennis tournament on Sunday, Aug. 18, 2013, in Mason, Ohio. Nadal won 7-6 (8), 7-6 (3). (AP Photo/Al Behrman)
Rafael Nadal of Spain reacts as he loses a point to Steve Darcis of Belgium during their Men's first round singles match at the All England Lawn Tennis Championships in Wimbledon, London, Monday, June 24, 2013. (AP Photo/Kirsty Wigglesworth)
Spain's Rafael Nadal clenches his fist after scoring against compatriot David Ferrer in the final of the French Open tennis tournament, at Roland Garros stadium in Paris, Sunday June 9, 2013. (AP Photo/Petr David Josek)
Serbia's Novak Djokovic clenches his fist after scoring against Spain's Rafael Nadal in their semifinal match at the French Open tennis tournament, at Roland Garros stadium in Paris, Friday June 7, 2013. (AP Photo/Michel Euler)
Spain's Rafael Nadal returns against Serbia's Novak Djokovic in their semifinal match at the French Open tennis tournament, at Roland Garros stadium in Paris, Friday June 7, 2013. (AP Photo/Christophe Ena)
Spain's Rafael Nadal returns against Switzerland's Stanislas Wawrinka in their quarterfinal match at the French Open tennis tournament, at Roland Garros stadium in Paris, Wednesday June 5, 2013. (AP Photo/Petr David Josek)
Spain's Rafael Nadal returns against Slovakia's Martin Klizan in their second round match at the French Open tennis tournament, at Roland Garros stadium in Paris, Friday, May 31, 2013. (AP Photo/Michel Spingler)