TMZSports.com

Khamzat Chimaev Believes Usman, Not Robert Whittaker, Toughest Test Of Career

Khamzat Chimaev has his hands full with Robert Whittaker -- the former UFC middleweight champion -- but, he doesn't believe it'll be the toughest test of his career ... 'cause that honor belongs to Kamaru Usman.

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