Czech Republic's Karolina Pliskova celebrates as she defeats China's Saisai Zheng during their first round match of the French Open tennis tournament at the Roland Garros stadium, Monday, May 29, 2017 in Paris. Pliskova won 7-5, 6-2. (AP Photo/Petr David Josek)
Caroline Wozniacki, of Denmark, serves to Karolina Pliskova, of the Czech Republic, during a tennis match at the Miami Open, Thursday, March 30, 2017 in Key Biscayne, Fla. (AP Photo/Wilfredo Lee)
Karolina Pliskova, of the Czech Republic, reacts after losing a point to Caroline Wozniacki, of Denmark, during a tennis match at the Miami Open, Thursday, March 30, 2017 in Key Biscayne, Fla. (AP Photo/Wilfredo Lee)
Caroline Wozniacki, of Denmark, serves to Karolina Pliskova, of the Czech Republic, during a tennis match at the Miami Open, Thursday, March 30, 2017 in Key Biscayne, Fla. (AP Photo/Wilfredo Lee)
Caroline Wozniacki, of Denmark, returns a shot from Karolina Pliskova, of the Czech Republic, during a tennis match at the Miami Open, Thursday, March 30, 2017 in Key Biscayne, Fla. (AP Photo/Wilfredo Lee)
Karolina Pliskova, of the Czech Republic, returns a shot to Svetlana Kuznetsova, of Russia, at the BNP Paribas Open tennis tournament, Friday, March 17, 2017, in Indian Wells, Calif. (AP Photo/Mark J. Terrill)
Svetlana Kuznetsova, of Russia, returns a shot to Karolina Pliskova, of the Czech Republic, at the BNP Paribas Open tennis tournament, Friday, March 17, 2017, in Indian Wells, Calif. (AP Photo/Mark J. Terrill)
Karolina Pliskova of Czech Republic returns the ball to Anastasia Pavlyuchenkova of Russia during the second day of Dubai Duty Free Tennis Championships in Dubai, United Arab Emirates, Monday, Feb. 16, 2015. (AP Photo/Kamran Jebreili)