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DALLAS, TX - FEBRUARY 03: Kei Nishikori (JPN) hits a forehand during the RBC Tennis Championships of Dallas on February 3, 2018 at the T Bar M Racquet Club in Dallas, Texas. (Photo by George Walker/Icon Sportswire via Getty Images)

DALLAS, TX - FEBRUARY 03: Kei Nishikori (JPN) hits a forehand during the RBC Tennis Championships of Dallas on February 3, 2018 at the T Bar M Racquet Club in Dallas, Texas. (Photo by George Walker/Icon Sportswire via Getty Images)