Stan Wawrinka of Switzerland in action against David Goffin of Belgium during their fourth round match for the Wimbledon Championships at the All England Lawn Tennis Club, in London, Britain, 06 July 2015. EPA/FACUNDO ARRIZABALAGA

Vasek Pospisil of Canada celebrates winning against Viktor Troicki of Serbia during their fourth round match for the Wimbledon Championships at the All England Lawn Tennis Club, in London, Britain, 06 July 2015. EPA/SEAN DEMPSEY

Andy Murray of Britain in action against Ivo Karlovic of Croatia in their fourth round match during the Wimbledon Championships at the All England Lawn Tennis Club, in London, Britain, 06 July 2015. EPA/ANDY RAIN

Venus (L) and Serena Williams of the US in between games in their fourth round match during the Wimbledon Championships at the All England Lawn Tennis Club, in London, Britain, 06 July 2015. EPA/ANDY RAIN

Nick Kyrgios of Australia returns to Richard Gasquet of France in their fourth round match during the Wimbledon Championships at the All England Lawn Tennis Club, in London, Britain, 06 July 2015. EPA/FACUNDO ARRIZABALAGA