Don't expect to see him in a cage tomorrow -- or anytime this year, for that matter -- but Shane Carwin is in the process of resuming his fighting career.

A laundry list of injuries caused the former UFC interim heavyweight champion to officially announce his retirement in 2013. He hasn't fought since June 2011, when he suffered a decision loss to Junior dos Santos at UFC 131.

Carwin, 41, says he initially thought he'd never come out of retirement, but his body has responded well to this five-year break. Last month, Carwin and his manager, Jason Genet, reached out to UFC matchmaker Joe Silva to discuss a comeback.

"Right now, there's a lot of paperwork to go through," Carwin told ESPN's 5 Rounds Podcast. "My son is getting into training, so I thought this was an opportunity to come back. I'm healthy. I feel good with the time off.

"It was a sad way for me to go out, with the back injuries and the knee, my neck -- everything. My body needed that break, and quite honestly, back then, the way we were training, I feel we probably trained too much. Too intense. We were sparring three times a week. A lot has revolutionized in the last five years. It's kind of changed the sport. I look at [training] schedules and they're not as demanding on the body [now]."

According to Genet, Carwin (12-2) had two fights left on his UFC contract when he retired. If, for whatever reason, the UFC isn't interested in Carwin's comeback, Genet anticipates the promotion would grant him a release to pursue other opportunities.

Those discussions are still in a very early phase. Under the UFC's anti-doping policy, which launched July 1 last year, a retired athlete wishing to resume his or her career must first be subject to a four-month testing window by the United States Anti-Doping Agency (USADA).

The UFC can waive that requirement under "exceptional circumstances," as it did for Brock Lesnar ahead of UFC 200, but Genet said Carwin is very willing to undergo four months of testing -- meaning there's no immediate rush for the UFC to book him a date and opponent.

"Shane wants to do it without any question marks," Genet said. "We spoke to Joe Silva, who told us what to do, who to talk to. We spoke to the legal department and [UFC Vice President of Athlete Health and Wellness] Jeff Novitzky. Jeff is ready to start the USADA process whenever we are. That's the easy part. We asked the legal department if they want to be in the Shane Carwin business and asked them another specific question I won't get into right now. We have not heard back on either question yet."

While his management sorts out the details, Carwin says his full focus now is on the gym. He intends to train with his former coach Leister Bowling, who is now the head coach of Colorado's Elevation Fight Team with striking coach Christian Allen and grappling coach Eliot Marshall.

In order to give his body proper rest, Carwin hasn't done any fight-specific training in years, but he is confident his skills haven't deteriorated. If he's proven wrong in the gym in the coming months, he'll rethink the idea of coming back -- but he doesn't anticipate that happening.

"I've told myself there's no guarantees," Carwin said. "If I get in the room and don't dominate like I used to, it's probably not a wise thing to go in there and fight someone near the top of the world. But if I am, I'm definitely going to be fighting.

"I knew when I saw Georges St-Pierre," who retired in late 2014, "what he was going through at the very end, I knew exactly how he felt. I was just worn out, stressed out, not fun anymore. Too many people in your pockets, demanding this and that. Everything became everything I didn't want this sport to become, if that makes sense. It was too much business, not so much my love for the sport. I grew old of it real quick."

When asked what caliber of opponent he'd want whenever he does return, Carwin laughed and said, "I'm not so sure I'd have a choice. I'm pretty sure they'd stick me in there [with the top]. And I'm OK with that."

A former collegiate wrestler and football player, Carwin rose to the top of the heavyweight division in 2010 by winning his first 12 professional fights in the first round. He won the UFC interim title by knocking out Frank Mir at UFC 111.

At UFC 116 in July 2011, Carwin fought Lesnar for the unified heavyweight title. He badly hurt Lesnar with punches in the opening round but tired in the next frame, where he lost via submission.

Carwin says he doesn't lose sleep over that loss, but he would gladly accept a chance to fight Lesnar again. Lesnar, who is under contract with the WWE, fought at UFC 200 last month and defeated Mark Hunt, but he failed a pair of drug tests. He is currently facing a potential two-year suspension.

"I'd always have interest in fighting that guy again, whether it be on the street or what," Carwin said. "I would like to get another shot at that. I don't know if that will happen. I'm not focused on him. I'm just focused on getting back there and doing the game I love so much."