NEW YORK, NY - SEPTEMBER 04: John Isner of The United States serves the ball during the men's singles quarter-final match against Juan Martin Del Potro of Argentina on Day Nine of the 2018 US Open at the USTA Billie Jean King National Tennis Center on September 4, 2018 in the Flushing neighborhood of the Queens borough of New York City. (Photo by Elsa/Getty Images)
