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NEW YORK, NEW YORK - AUGUST 30: Novak Djokovic of Serbia and Denis Kudla of the United States shake hands following their Men's Singles third round match on day five of the 2019 US Open at the USTA Billie Jean King National Tennis Center on August 30, 2019 in Queens borough of New York City. (Photo by Katharine Lotze/Getty Images)

NEW YORK, NEW YORK - AUGUST 30: Novak Djokovic of Serbia and Denis Kudla of the United States shake hands following their Men's Singles third round match on day five of the 2019 US Open at the USTA Billie Jean King National Tennis Center on August 30, 2019 in Queens borough of New York City. (Photo by Katharine Lotze/Getty Images)