Japan Open: Kei Nishikori retires from tennis after defeat by Frances Tiafoe in Tokyo

A tearful Kei Nishikori said he "kept fighting right to the end" as the former world number four ended his professional career at the Japan Open.

Nishikori, known as one of the best players to never win a Grand Slam, lost 6-4 6-4 to world number eigh... [650 chars]

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