Serena Williams of the USA celebrates a point against Margarita Gasparyan of Russia during their first round match of the Wimbledon Championships at the All England Lawn Tennis Club in London, Britain, 29 June 2015. EPA/PETER KLAUNZER NO SALES/NO ARCHIVES

Joao Sousa of Portugal returns to Stan Wawrinka of Switzerland in their first round match during the Wimbledon Championships at the All England Lawn Tennis Club, in London, Britain, 29 June 2015. EPA/FACUNDO ARRIZABALAGA

Belinda Bencic (front) of Switzerland returns the ball to Tsvetana Pironkova (back) of Bulgaria during their first round match of the Wimbledon Championships at the All England Lawn Tennis Club, in London, Britain, 29 June 2015. EPA/PETER KLAUNZER

Tommy Haas of Germany in action against Dusan Lajovic of Serbia during their first round match for the Wimbledon Championships at the All England Lawn Tennis Club, in London, Britain, 29 June 2015. EPA/ANDY RAIN

Lleyton Hewitt of Australia in action against Jarkko Nieminen of Finland during their first round match for the Wimbledon Championships at the All England Lawn Tennis Club, in London, Britain, 29 June 2015. EPA/ANDY RAIN