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BEIJING, CHINA - OCTOBER 03: Andrey Rublev of Russia returns a shot against Jack Sock of the United States in his Men's Single First round match on day four of the 2017 China Open at the China National Tennis Centre on October 3, 2017 in Beijing, China. (Photo by Etienne Oliveau/Getty Images)

BEIJING, CHINA - OCTOBER 03:  Andrey Rublev of Russia returns a shot against Jack Sock of the United States in his Men's Single First round match on day four of the 2017 China Open at the China National Tennis Centre on October 3, 2017 in Beijing, China.  (Photo by Etienne Oliveau/Getty Images)