“I am going to pull out of the fight with Roy Nelson,” Carwin announced on his website. “As many of you know I have been having some back pain. I had an MRI yesterday and I have some damage that may really require surgery. If the doctors do not have to perform surgery then I will be out 8-12 weeks. If they do have to perform surgery I do not know how long I will be out of action.”
Carwin (12-1) challenged Brock Lesnar for the heavyweight title in his most-recent fight in July and nearly finished the champ in the opening round only to be submitted in the second for his first career loss.
Nelson (15-5), the winner of The Ultimate Fighter 10, dropped a unanimous decision to upcoming challenger Junior dos Santos in August following back-to-back wins over Brendan Schaub and Stefan Struve.
The UFC 125 fight card is headlined by a rematch between light champion Frankie Edgar and Gray Maynard, but it’s not yet known who will replace Carwin in the co-main event.