LAS VEGAS -- UFC heavyweight contender Shane Carwin says he's pulling out of a high-profile New Year's Day bout with a back injury.
Carwin (12-1) announced his decision on his blog Tuesday. He was expected to fight Roy Nelson in the co-main event at UFC 125 in the MGM Grand Garden.
He says he has unspecified damage to his back that may require surgery.
Carwin was unbeaten until his second-round submission loss to Brock Lesnar last July.
The UFC has no obvious replacement for Carwin in his fight against Nelson, which could have set up the winner with a chance to face new heavyweight champion Cain Velasquez later in 2011.