Urszula Radwanska of Poland returns the ball to Lesia Tsurenko of Ukraine during their final match of the WTA Istanbul Cup tennis tournament in Istanbul, Turkey, 26 July 2015. EPA/SEDAT SUNA

Lesia Tsurenko of Ukraine returns the ball to Urszula Radwanska of Poland during their final match of the WTA Istanbul Cup tennis tournament in Istanbul, Turkey, 26 July 2015. EPA/SEDAT SUNA

Karin Knapp of Italy returns the ball to Samantha Stosur of Australia during their final match of the WTA tennis tournament in Bad Gastein, Austria, 26 July 2015. EPA/EXPA/JFK

Lesia Tsurenko of Ukraine celebrates with her trophy after defeating Urszula Radwanska of Poland in the final match for the WTA Istanbul Cup tennis tournament in Istanbul, Turkey, 26 July 2015. EPA/SEDAT SUNA

Tommy Robredo of Spain in action against Benoit Paire of France at the Skistar Swedish Open in Bastad, Sweden, on Sunday, July 26, 2015. EPA/Bjoern Larsson Rosvall

Benoit Paire (FRA) celebrates his victory against Tommy Robredo (ESP) after the final of the Skistar Swedish Open in Bastad, Sweden, on Sunday, July 26, 2015. EPA/Bjoern Larsson Rosvall

Former tennis player Ilie Nastase (L) of Romania plays a ball next to Alex Corretja of Spain during an exhibition match at the Suisse Open tennis tournament in Gstaad, Switzerland, 26 July 2015. The tournament takes place from 27 July through 02 August 2015. EPA/PETER SCHNEIDER