For all intents and purposes, Brock Lesnar ’s life in the UFC was short-lived. But his impact on the heavyweight division was fairly significant. Lesnar won the heavyweight title in just his fourth pro fight when he took out Randy Couture with a second-round TKO at UFC 91 in November 2008. That win came just nine months after he was submitted by Frank Mir in his second pro fight. But at UFC 100 in July 2009, Lesnar got a chance for revenge against Mir in a title unification bout
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Video: Was Brock Lesnar’s UFC win over Frank Mir the biggest of his MMA career? – MMA Junkie