MELBOURNE, VIC - JANUARY 26: Roger Federer of Switzerland returns the ball during the Semi-finals of the 2017 Australian Open on January 26, 2017, at Melbourne Park Tennis Centre in Melbourne, Australia.(Photo by Jason Heidrich/Icon Sportswire via Getty Images)
MELBOURNE, VIC - JANUARY 26: Stan Wawrinka of Switzerland returns the ball during the Semi-finals of the 2017 Australian Open on January 26, 2017, at Melbourne Park Tennis Centre in Melbourne, Australia.(Photo by Jason Heidrich/Icon Sportswire via Getty Images)
MELBOURNE, AUSTRALIA - JANUARY 27: Grigor Dimitrov of Bulgaria plays a backhand in his semifinal match against Rafael Nadal of Spain on day 12 of the 2017 Australian Open at Melbourne Park on January 27, 2017 in Melbourne, Australia. (Photo by Michael Dodge/Getty Images)
