Serena Williams of the US returns to compatriot Christina McHale in their second round match during the Wimbledon Championships at the All England Lawn Tennis Club, in London, Britain, 01 July 2016. EPA/GERRY PENNY

Jo-Wilfried Tsonga of France plays Andy Murray of Britain in their quarter final match during the Wimbledon Championships at the All England Lawn Tennis Club, in London, Britain, 06 July 2016. EPA/ANDY RAIN

Marcus Willis of Britain celebrates a winner against Roger Federer of Switzerland during their second round match at the Wimbledon Championships at the All England Lawn Tennis Club, in London, Britain, 29 June 2016. EPA/FACUNDO ARRIZABALAGA

Coco Vandeweghe of the USA returns to Roberta Vinci of Italy during their third round match at the Wimbledon Championships at the All England Lawn Tennis Club, in London, Britain, 03 July 2016 EPA/ANDY RAIN

Roger Federer of Switzerland returns to Milos Raonic of Canada in their semi final match during the Wimbledon Championships at the All England Lawn Tennis Club, in London, Britain, 08 July 2016 EPA/CLIVE BRUNSKILL

Feliciano Lopez of Spain returns to Nick Kyrgios of Australia in their third round match during the Wimbledon Championships at the All England Lawn Tennis Club, in London, Britain, 03 July 2016. EPA/GERRY PENNY

Nick Kyrgios of Australia celebrates a set point winner over Feliciano Lopez of Spain in their third round match during the Wimbledon Championships at the All England Lawn Tennis Club, in London, Britain, 02 July 2016. EPA/FACUNDO ARRIZABALAGA