CINCINNATI, OH - AUGUST 20: Novak Djokovic of Serbia returns a shot to David Goffin of Belgium during the Western & Southern Open at the Linder Family Tennis Center on August 20, 2015 in Cincinnati, Ohio. (Photo by Rob Carr/Getty Images)
CINCINNATI, OH - AUGUST 20: Novak Djokovic of Serbia returns a shot to David Goffin of Belgium during the Western & Southern Open at the Linder Family Tennis Center on August 20, 2015 in Cincinnati, Ohio. (Photo by Rob Carr/Getty Images)