NEW YORK, NY - AUGUST 25:   Novak Djokovic of Serbia returns a shot against Diego Schwartzman of Argentina during their men's singles first round match on Day One of the 2014 US Open at the USTA Billie Jean King National Tennis Center on August 25, 2014  in the Flushing neighborhood of the Queens borough of New York City.  (Photo by Julian Finney/Getty Images)