NEW YORK, NY - SEPTEMBER 09: Novak Djokovic of Serbia returns the ball during his men's Singles finals match against Juan Martin del Potro of Argentina on Day Fourteen of the 2018 US Open at the USTA Billie Jean King National Tennis Center on September 9, 2018 in the Flushing neighborhood of the Queens borough of New York City. (Photo by Elsa/Getty Images)
