Is it finally, just maybe, Todd Duffee time?

Health issues and self doubt forced Todd Duffee to reconsider his place in the MMA realm. Ed Mulholland for ESPN

LAS VEGAS -- Any time Todd Duffee touches down in Las Vegas these days, he gets a little nostalgic. The big guy can't help it.

This city will always represent something of a crossroads in his life. He moved here in 2009 as an undefeated 24-year-old prospect, coming off a seven-second knockout in his UFC debut.

He moved to Las Vegas to accomplish two things: climb the heavyweight rankings in the UFC and earn a degree at the University of Nevada Las Vegas.

Five years later, neither has happened for Duffee -- but heading into what will be his fourth UFC fight against Anthony Hamilton (13-3) at UFC 181 at Mandalay Bay Events Center, the 28-year-old believes he's finally ready to change that.

"Nostalgia is a weird emotion," Duffee told ESPN.com. "You're happy but there's that sad part, too, you know what I mean? It's a weird emotion. It's positive for me to feel that, though, because it's a reminder that I have been through the MMA scene, man. I have done and experienced everything, and that gives me a boost."

Duffee (8-2) isn't kidding when he says he's been through everything.

Following that seven-second knockout over Tim Hague in August 2009, Duffee was pegged a rising star in the UFC. Upon his arrival in Las Vegas, he shared a training room (and coaches) with a living legend in Randy Couture.

On top of his fighting talent, the kid showed maturity by enrolling at UNLV. Invest in the future. Good head on his shoulders, as they say.

But Duffee's luck went south in Vegas. He realized he couldn't juggle professional fighting and full-time studies and dropped out of classes weeks after the move.

He lost his second fight in the UFC in stunning fashion to Mike Russow in May 2010. Shortly after, he drew the ire of UFC president Dana White, who questioned his attitude and ultimately cut him from the roster.

In December 2010, Duffee fought Alistair Overeem at a K-1 event and lost via knockout in 19 seconds. He wouldn't fight again for 16 months and changed camps multiple times. In MMA circles, the term "head case" started to follow him.

Looking back, Duffee doesn't feel he was ever difficult to work with and believes he's generally been misunderstood, but he admits his mental state wasn't right.

One way to put it is he sabotaged his own success by wanting it too much. He weighed himself down with internal pressure, and it disrupted every aspect of his career.

"I was pretty insecure," Duffee said. "I've always been dedicated to athletics. I've sold my soul to sports. I was in the gym every day, overtraining. [After the Hague knockout] my mentality was, 'Don't f--- this up.' It wasn't a Conor McGregor, 'I've got this.' It was always, 'Don't f--- this up.' ... I was tense. I was tight. It showed in my interviews and it showed in my personality. Everybody thought I was this giant d---.

"[My career] has been hell, hell, hell -- because of my mindset. I've wanted it so bad. I had a lot of good times, but I could never really be there for them because I was so focused. I've been like that since I was 13. Like, 'Oh you guys are going out tonight? I'm going to run sprints.' I don't say that to make everyone think I'm a hard worker. It was crazy. It was stupid. It's been detrimental for me."

In 2012, Duffee nearly called it quits in MMA. He says he was one day away from signing a contract to compete in kickboxing overseas -- a career change he wasn't enthusiastic about, but felt backed into.

And then, by chance, the UFC needed a last-minute replacement at UFC 155 and Duffee got the call. He re-signed with the promotion and, just as he did in August 2009, knocked out his opponent in the first round, creating plenty of buzz in doing so.

Duffee was back. He was training with top-tier heavyweights at American Kickboxing Academy, and he says he'd reached an understanding of himself as "a man and a fighter." Mentally, he'd never been better.

One month later, though, Duffee woke up with a stabbing pain in his back. He lost strength in one arm. He told the UFC he'd need time to figure out what was going on.

Several evaluations and consultations later, Duffee was diagnosed with Parsonage-Turner syndrome, a rare nerve disorder which can cause pain, numbness and loss of motor function, among other symptoms.

Long story short, Duffee overcame the disorder enough to return to the Octagon this weekend, but not before it stole two years of his athletic prime. He also left AKA to run a group fitness program in Florida.

Today, you might say he's come full circle. He's rejoined American Top Team -- the same team he parted ways with when he moved to Las Vegas in 2009.

He's five years older, but his place in the sport remains eerily similar to what it once was: A very, very scary heavyweight prospect.

The biggest difference in Duffee now is that he believes that. He's got that stability he desperately wanted earlier in his career and he's focused on enjoying the fight in front of him.

"I feel stable," Duffee said. "I'm not huge, but I have enough people who are interested in me for some reason. I'm that anomaly, where I can hide under the table for two years like I just did and people are still interested enough for me to get on the main card of UFC 181. No disrespect to Anthony, but I don't think he's the reason we're on the main card. My honest perspective is that I'm the reason.

"I've got this one opportunity in front of me, and that's all I'm thinking about. This is it."