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BRISBANE, AUSTRALIA - JANUARY 08: Roger Federer of Switzerland plays a forehand in his quarter final match against Grigor Dimitrov of Bulgaria during day six of the 2016 Brisbane International at Pat Rafter Arena on January 8, 2016 in Brisbane, Australia. (Photo by Chris Hyde/Getty Images)

BRISBANE, AUSTRALIA - JANUARY 08:  Roger Federer of Switzerland plays a forehand in his quarter final match against Grigor Dimitrov of Bulgaria during day six of the 2016 Brisbane International at Pat Rafter Arena on January 8, 2016 in Brisbane, Australia.  (Photo by Chris Hyde/Getty Images)