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NEW YORK, NY - AUGUST 30: Yen-Hsun Lu of Taipei serves against Ivo Karlovic of Croatiav 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 Queens borough of New York City. (Photo by Mike Stobe/Getty Images for USTA)

NEW YORK, NY - AUGUST 30:  Yen-Hsun Lu of Taipei serves against Ivo Karlovic of Croatiav 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 Queens borough of New York City.  (Photo by Mike Stobe/Getty Images for USTA)