Sloane Stephens, of the U.S, returns the ball to China's Peng Shuai during the first round match of the French Open tennis tournament at the Roland Garros stadium, in Paris, France, Tuesday, May 27, 2014. (AP Photo/Darko Vojinovic)
Sloane Stephens, of the U.S, returns the ball to China's Peng Shuai during the first round match of the French Open tennis tournament at the Roland Garros stadium, in Paris, France, Tuesday, May 27, 2014. (AP Photo/Darko Vojinovic)
Na Li from China returns the ball during a Madrid Open tennis tournament match against Sloane Stephens from U.S. in Madrid, Spain, Thursday, May 8, 2014 . (AP Photo/Daniel Ochoa de Olza)
Na Li from China returns the ball during a Madrid Open tennis tournament match against Sloane Stephens from U.S. in Madrid, Spain, Thursday, May 8, 2014 . (AP Photo/Daniel Ochoa de Olza)
Na Li from China serves the ball during a Madrid Open tennis tournament match against Sloane Stephens from the U.S. in Madrid, Spain, Thursday, May 8, 2014 . (AP Photo/Daniel Ochoa de Olza)
Na Li from China serves the ball during a Madrid Open tennis tournament match against Sloane Stephens from the U.S. in Madrid, Spain, Thursday, May 8, 2014 . (AP Photo/Daniel Ochoa de Olza)
Na Li from China serves the ball during a Madrid Open tennis tournament match against Sloane Stephens from U.S. in Madrid, Spain, Thursday, May 8, 2014 . (AP Photo/Daniel Ochoa de Olza)