Kei Nishikori

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Benjamin Becker, of Germany, draws a bead on the ball as he prepares to hit a return to Kei Nishikori, of Japan, in a second-round match at the U.S. National Indoor Tennis Championships, Wednesday, Feb. 12, 2014, in Memphis, Tenn. (AP Photo/Rogelio V. Solis)

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Kei Nishikori, of Japan, watches a return to Benjamin Becker, of Germany, at the U.S. National Indoor Tennis Championships on Wednesday, Feb. 12, 2014, in Memphis, Tenn. (AP Photo/Rogelio V. Solis)

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Frank Dancevic of Canada reacts after he lost a point against Kei Nishikori of Japan during their 1st round of Davis Cup World Group tennis in Tokyo, Sunday, Feb. 2, 2014. (AP Photo/Shizuo Kambayashi)

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Frank Dancevic, right, of Canada greets Japan's team captain Minoru Ueda, center, and Kei Nishikori after he pulled out of a match against Nishikori due to injuries, at their 1st round of Davis Cup World Group tennis in Tokyo, Sunday, Feb. 2, 2014. (AP Photo/Shizuo Kambayashi)

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Frank Dancevic of Canada reacts before pulling out of a match against Kei Nishikori of Japan, due to injuries, at their 1st round of Davis Cup World Group tennis in Tokyo, Sunday, Feb. 2, 2014. (AP Photo/Shizuo Kambayashi)

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Frank Dancevic of Canada, center facing, reacts before pulling out of a match against Kei Nishikori of Japan, due to injuries, during their 1st round of Davis Cup World Group tennis in Tokyo, Sunday, Feb. 2, 2014. (AP Photo/Shizuo Kambayashi)

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Kei Nishikori of Japan returns the ball against Frank Dancevic of Canada during their 1st round of Davis Cup World Group tennis in Tokyo, Sunday, Feb. 2, 2014. (AP Photo/Shizuo Kambayashi)

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Kei Nishikori of Japan reacts after getting a point against Frank Dancevic of Canada during their 1st round of Davis Cup World Group tennis in Tokyo, Sunday, Feb. 2, 2014. (AP Photo/Shizuo Kambayashi)

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Frank Dancevic of Canada returns the ball against Kei Nishikori of Japan during their 1st round of Davis Cup World Group tennis in Tokyo, Sunday, Feb. 2, 2014. (AP Photo/Shizuo Kambayashi)