TORONTO -- Veteran UFC heavyweight Shane Carwin has retired.
"Officially retired 2day:-) thank you to my family, friends and fans! .dreambig GOD BLESS!!!" tweeted the 38-year-old MMA fighter.
Carwin (12-2) went 4-2 in the UFC and won the interim heavyweight title when he defeated Frank Mir at UFC 111 in March 2010. He lost a subsequent title shot to Brock Lesnar at UFC 116 in July 2010.
Carwin dominated Lesnar in the early going, holding a 39-3 edge in significant strikes according to FightMetric. But, with referee Josh Rosenthal hovering nearby, a downed and desperate Lesnar somehow survived the round -- and then rallied to submit an exhausted Carwin in the second round
A former NFL prospect and NCAA Division II champion wrestler, Carwin kept his day job as an engineer for Colorado's North Weld County Water while fighting.
His first 10 MMA bouts lasted just 11 minutes 13 seconds, during which time the heavyweight from Greeley, Colo., knocked out five opponents and submitted another five.
Eleven of his wins came under two minutes.
The six-foot-two 265-pounder made his UFC debut at UFC 84 -- in a rare engineer versus lawyer showdown -- when he knocked out Christian Wellisch in 44 seconds with a highlight-reel right to the chin that buckled Wellisch's legs and sent his mouthpiece flying across the cage.
His last fight was a decision loss to Brazilian slugger Junior Dos Santos at UFC 131 in Vancouver in June 2011.
Carwin was slowed by neck and knee problems but was a tough customer when healthy. Gabriel Gonzaga broke his nose at UFC 96 but Carwin regathered his wits and stopped him in the first round.