Serena Williams of the US reacts during her quarter finals match against Maria Sharapova of Russia at the Australian Open tennis tournament in Melbourne, Australia, 26 January 2016. EPA/MAST IRHAM

Milos Raonic of Canada reacts after defeating Stan Wawrinka of Switzerland in their fourth round match on day eight of the Australian Open tennis tournament in Melbourne, Australia, 25 January 2016. EPA/FILIP SINGER

Angelique Kerber of Germany celebrates a winner during her quarter final match against Victoria Azarenka of Belarus at the Australian Open tennis tournament in Melbourne, Australia, 27 January 2016. EPA/FILIP SINGER

Andy Murray of the United Kingdom reacts during his fourth round match against Bernard Tomic of Australia at the Australian Open tennis tournament in Melbourne, Australia, 25 January 2016. EPA/JULIAN SMITH

Maria Sharapova of Russia reacts as she plays against Serena Williams of the US during their quarter finals round on day nine of the Australian Open tennis tournament in Melbourne, Australia, 26 January 2016. EPA/LUKAS COCH

Australian tennis fans dressed in Australian bush hats strung with corks to keep off annoying flys and the nations green and gold colours, shout ‘ oi oi oi’ the Aussie slogan for court side encouragement, on the opening day of the Australian Open, at Melbourne Park, Melbourne, Australia, Monday, 17 January 2005. The Australian Open celebrates its centenary this year, with world ranked players including wrold number one Roger Federer from Switzerland and Lindsay Davenport from the US competing in the two week Grand Slam competition. EPA/BARBARA WALTON