Only 69 times in MMA history has a professional fight went 5 rounds (or more) and the fight was finished before going to a decision.
Anderson Silva vs. Chael Sonnen will only be the second time in history in which a rematch occured afterward. The first, being a rematch between Jorge Santiago and Kazuo Misaki, where in the first match-up, Santiago won by submission in the 5th round — sound familiar? Amazingly, Santiago won the rematch in the 5th round also, but that time by TKO.