NEW YORK, NY - SEPTEMBER 13:  Novak Djokovic of Serbia, right, and Roger Federer of Switzerland celebrate with their trophies after their Men's Singles Final match on Day Fourteen of the 2015 US Open at the USTA Billie Jean King National Tennis Center on September 13, 2015 in the Flushing neighborhood of the Queens borough of New York City. Djokovic defeated Federer 6-4, 5-7, 6-4, 6-4.  (Photo by Clive Brunskill/Getty Images)