Former UFC heavyweight contender Shane Carwin announces his retirement on Twitter

After 12-2 career, UFC heavyweight fighter Shane Carwin announced his retirement on Twitter on Tuesday night.

Of Carwin's 12 wins, not one went to the judges. He had seven knockouts and five submissions. He hasn't been in the cage since 2011. The last time he was in the spotlight was in the fall of 2012, when he was a coach on "The Ultimate Fighter." Unfortunately, his knee was injured before he could fight opposing coach Roy Nelson.

I remember hearing about Carwin well before I saw him fight. It was back when preliminary fights weren't aired. Everyone who had watched him fight couldn't stop talking about this guy who quickly knocked out Christian Wellisch and Neil Wain. Then at UFC 96, I watched him absolutely destroy Gabriel Gonzaga in just over a minute. He hadn't been overhyped. After that, he knocked out Frank Mir in the first round of their bout.

What most MMA fans will remember about Carwin is that he came within seconds of taking out the then-invincible Brock Lesnar at UFC 116. But after losing to Lesnar in the second round, a dropped decision to Junior dos Santos at UFC 131 and a host of injuries, Carwin has decided to hang up his extra-large gloves.