Dominic Thiem of Austria plays a shot against David Goffin of Belgium during their third round match on day five of the Australian Open tennis tournament in Melbourne, Australia, 22 January 2016. EPA/JOE CASTRO

Novak Djokovic of Serbia plays a shot against Andreas Seppi of Italy during their third round natch at the Australian Open tennis tournament in Melbourne, Australia, 22 January 2016. EPA/DAVID CROSLING

Maria Sharapova of Russia serves to Lauren Davis of the United States during their third round match on day five of the Australian Open tennis tournament in Melbourne, Australia, 22 January 2016. EPA/TRACEY NEARMY

Ball boys mop up Rod Laver Arena during the third round match between Roger Federer of Switzerland and Grigor Dimitrov of Bulgaria at the Australian Open tennis tournament in Melbourne, Australia, 22 January 2016. EPA/TRACEY NEARMY

Roger Federer of Switzerland plays a forehand to Grigor Dimitrov of Bulgaria during their third round match at the Australian Open tennis tournament in Melbourne, Australia, 22 January 2016. EPA/TRACEY NEARMY

Kei Nishikori of Japan plays a shot against Guillermo Garcia-Lopez of Spain during their third round match on day five of the Australian Open tennis tournament in Melbourne, Australia, on 22 January 2016. The Australian Open tennis tournament will go from the 18th of January until the 31st of January 2016 and is Australia’s foremost annual tennis event. EPA/DAVID CROSLING