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ZHUHAI, CHINA - OCTOBER 31: Daria Kasatkina of Russia returns a shot against Madison Keys of the United States during their women's singles match on day 2 of the 2018 WTA Elite Trophy Zhuhai at Hengqin Tennis Center on October 31, 2018 in Zhuhai, China. (Photo by Zhe Ji/Getty Images)

ZHUHAI, CHINA - OCTOBER 31:  Daria Kasatkina of Russia returns a shot against Madison Keys of the United States during their women's singles match on day 2 of the 2018 WTA Elite Trophy Zhuhai at Hengqin Tennis Center on October 31, 2018 in Zhuhai, China.  (Photo by Zhe Ji/Getty Images)