Rafael Nadal, of Spain, hits a return to Fabio Fognini, of Italy, during a men's semifinal match at the Miami Open tennis tournament, Friday, March 31, 2017, in Key Biscayne, Fla. (AP Photo/Lynne Sladky)
Jack Sock, of the United States, hits a backhand against Rafael Nadal, of Spain, during a quarterfinal match at the Miami Open tennis tournament, Wednesday, March 29, 2017, in Key Biscayne, Fla. (AP Photo/Mario Houben)
Rafael Nadal, of Spain, plays a forehand against Jack Sock, of the United States, during a quarterfinal match at the Miami Open tennis tournament, Wednesday, March 29, 2017, in Key Biscayne, Fla. (AP Photo/Mario Houben)
Rafael Nadal, of Spain, serves the ball to Philipp Kohlschreiber, of Germany, during the Miami Open tennis tournament, Sunday, March 26, 2017, in Key Biscayne, Fla. (AP Photo/Luis M. Alvarez)
Philipp Kohlschreiber, of Germany, returns the ball to Rafael Nadal, of Spain, during the Miami Open tennis tournament, Sunday, March 26, 2017, in Key Biscayne, Fla. (AP Photo/Luis M. Alvarez)
Rafael Nadal, of Spain, returns the ball to Philipp Kohlschreiber, of Germany, during the Miami Open tennis tournament, Sunday, March 26, 2017, in Key Biscayne, Fla. (AP Photo/Luis M. Alvarez)
Rafael Nadal, of Spain, returns the ball to Dudi Sela, of Israel, during the Miami Open tennis tournament, Friday, March 24, 2017, in Key Biscayne, Fla. (AP Photo/Luis M. Alvarez)
Rafael Nadal, of Spain, gestures after defeating Dudi Sela, of Israel, during the Miami Open tennis tournament, Friday, March 24, 2017, in Key Biscayne, Fla. (AP Photo/Luis M. Alvarez)
Roger Federer, of Switzerland, celebrates after beating Rafael Nadal, of Spain, at the BNP Paribas Open tennis tournament, Wednesday, March 15, 2017, in Indian Wells, Calif. (AP Photo/Mark J. Terrill)
Roger Federer, of Switzerland, returns a shot against Rafael Nadal, of Spain, at the BNP Paribas Open tennis tournament, Wednesday, March 15, 2017, in Indian Wells, Calif. (AP Photo/Mark J. Terrill)
Rafael Nadal, of Spain, serves to Roger Federer, of Switzerland, at the BNP Paribas Open tennis tournament, Wednesday, March 15, 2017, in Indian Wells, Calif. (AP Photo/Mark J. Terrill)
Roger Federer, of Switzerland, returns a shot to Rafael Nadal, of Spain, at the BNP Paribas Open tennis tournament, Wednesday, March 15, 2017, in Indian Wells, Calif. (AP Photo/Mark J. Terrill)
Fernando Verdasco, of Spain, returns a shot to Rafael Nadal, of Spain, at the BNP Paribas Open tennis tournament, Tuesday, March 14, 2017, in Indian Wells, Calif. (AP Photo/Mark J. Terrill)
Rafael Nadal, of Spain, reacts after losing a point to Fernando Verdasco, of Spain, at the BNP Paribas Open tennis tournament, Tuesday, March 14, 2017, in Indian Wells, Calif. (AP Photo/Mark J. Terrill)
Fernando Verdasco, of Spain, returns a shot to Rafael Nadal, of Spain, at the BNP Paribas Open tennis tournament, Tuesday, March 14, 2017, in Indian Wells, Calif. (AP Photo/Mark J. Terrill)
Rafael Nadal, of Spain, returns a shot to Fernando Verdasco, of Spain, at the BNP Paribas Open tennis tournament, Tuesday, March 14, 2017, in Indian Wells, Calif. (AP Photo/Mark J. Terrill)
Rafael Nadal, of Spain, hits to Guido Pella, of Argentina, at the BNP Paribas Open tennis tournament, Sunday, March 12, 2017, in Indian Wells, Calif. (AP Photo/Mark J. Terrill)
Rafael Nadal, of Spain, celebrates his win against Guido Pella, of Argentina, at the BNP Paribas Open tennis tournament, Sunday, March 12, 2017, in Indian Wells, Calif. (AP Photo/Mark J. Terrill)
Rafael Nadal of Spain warps ice towels around his face during a break in his first round match against compatriot Fernando Verdasco at the Australian Open tennis championships in Melbourne, Australia, Tuesday, Jan. 19, 2016.(AP Photo/Aaron Favila)
Rafael Nadal of Spain walks after losing the singles match against Dustin Brown of Germany, at the All England Lawn Tennis Championships in Wimbledon, London, Thursday July 2, 2015. (AP Photo/Pavel Golovkin)