NEW YORK, NY - SEPTEMBER 07: Juan Martin del Potro of Argentina returns the ball during his men's singles semi-final match against Rafael Nadal of Spain on Day Twelve of the 2018 US Open at the USTA Billie Jean King National Tennis Center on September 7, 2018 in the Flushing neighborhood of the Queens borough of New York City. (Photo by Julian Finney/Getty Images)
