UFC heavyweight Shane Carwin announced today that he will be pulling out of a fight with Roy Nelson that had been scheduled to take place at UFC 125.

Carwin (12-1) was the last man to fight former UFC heavyweight Brock Lesnar before Lesnar lost his belt to challenger Cain Velasquez at UFC 121. That fight featured a fierce early onslaught by Carwin before Lesnar came back in the second round to win by submission over his clearly exhausted opponent.

Carwin's upcoming fight with Nelson (15-5) was expected to be his first test on the road back to title contention, but it appears it will no longer take place due to a nagging back injury that Carwin revealed for the first time today. 

"I am going to pull out of the fight with Roy Nelson," Carwin said in his blog on Shane-Carwin.com. "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."

The timing of the announcement comes just days after Lesnar's defeat at the hands of Velasquez, and will surely cause some speculation among fans over it's potential impact not only on Carwin's health, but on Lesnar's next opponent as well.

Carwin is hoping to return to full health before he commits to his next fight, and has carefully considered his difficult decision to withdraw from the matchup with Nelson.

"I was really looking forward to fighting again and obviously this is a very disappointing turn of events," Carwin stated. "My manager said 'You can't fight the best fighters in the world with just heart, it is time to stop limping to the top of the mountain and get healthy so you can climb it on your terms.' I have been up all night thinking about this decision and what I may be missing by making it. In the end my family and manager are right. I owe myself, I owe my fans the best show I can give them. I need to get healthy. I am going to be speaking with the surgeon this week about the surgery. My thoughts are if the surgery fixes it why add 8-12 weeks of physical therapy, epidurals and traction if surgery may still be needed."

For Carwin, his layoff from fighting will at least come with a silver lining.

"The good news is the doctors said I can work on my cardio (they must have seen my last fight lol) with this injury," Carwin joked before striking a more serious tone. "No one wants to get me back to winning more than me. I just need to be healthy to do it."