NEW YORK, NY - AUGUST 30: Juan Martin del Potro of Argentina serves to Diego Schwartzman of Argentina during his first round Men's Singles match on Day Two of the 2016 US Open at the USTA Billie Jean King National Tennis Center on August 30, 2016 in the Flushing neighborhood of the Queens borough of New York City. (Photo by Elsa/Getty Images)

NEW YORK, NY - AUGUST 30:  Juan Martin del Potro of Argentina serves to Diego Schwartzman of Argentina during his first round Men's Singles match on Day Two of the 2016 US Open at the USTA Billie Jean King National Tennis Center on August 30, 2016 in the Flushing neighborhood of the Queens borough of New York City.  (Photo by Elsa/Getty Images)