It's been nearly two full years since Shane Carwin last fought in the UFC, and more than three years since his last victory. The former interim heavyweight champion has seemingly ended his MMA career through his Twitter account.
Officially retired 2day:-) thank you to my family, friends and fans! #dreambig GOD BLESS!!!— Shane Carwin (@ShaneCarwin) May 8, 2013
He never specified what he's retiring from -- he's also an engineer -- but the UFC retweeted him so I would assume that he means he will no longer compete in MMA.
Carwin ends his career with a record of 12-2, with all 12 finishes coming by 1st round KO or submission. His biggest achievement was KOing Frank Mir at UFC 111 to win the interim heavyweight belt. This led to a title unification bout with Brock Lesnar at UFC 116, where he dominated Lesnar in round 1 only to run out of gas and lose by submission in the next round.
After losing to Brock, Carwin's fight schedule had altered significantly. He was scheduled to fight Roy Nelson at UFC 125 but pulled out due to a back injury. He was also due to face the legendary Jon Olav Einemo at UFC 131, but when Brock Lesnar pulled out of his main event fight with Junior dos Santos, Carwin stepped up for (then) the only man to defeat him. It was a lopsided contest, but a bloodied and battered Shane made it to the final bell to take a decision loss.
Injuries have famously prevented Carwin from competing again since the JDS loss; he was given a coaching gig on TUF 16 opposite Roy Nelson, with the two strikers set to meet last December. However, a knee injury forced Carwin off the TUF 16 Finale and now it looks like he will hang up those humongous gloves at the age of 38.