Heavyweight is a notoriously unpredictable division in MMA, but 2015 has seen the division completely turned on its head.

One of the key stories among the big men has been the return of former UFC champions Frank Mir (18-9 MMA, 16-9 UFC) and Andrei Arlovski (24-10 MMA, 13-4 UFC) to the brink of title contention. After public cries for both men to retire after falling on hard times, they meet in Saturday’s UFC 191 co-headliner with Arlovski ranked No. 5 and Mir No. 11 in the NOS Energy Drink MMA heavyweight rankings. A win could position either man for a crack at the UFC title, a belt currently held by Fabricio Werdum in 2015’s other big heavyweight surprise.

UFC 191 takes at Las Vegas’ MGM Grand Garden Arena. The bout airs on pay-per-view following prelims on FOX Sports 1 and UFC Fight Pass.

In February 2014, Mir had suffered his fourth consecutive loss when Alistair Overeem beat him by unanimous decision. It seemed as though Mir had little left to give at the highest end of the sport, and 13 years of MMA mileage on his body and seven knockout losses had many fans and media members worried about his future.

Mir silenced many of his critics with back-to-back knockout wins over Antonio Silva and Todd Duffee. For Mir’s head trainer, Ricky Lundell, his 2015 resurgence shows just how much heart Mir has.

“Frank’s been great to work with lately,” Lundell told MMAjunkie. “We were on a low streak for a while, and that’s always difficult for any fighter. But let me tell you why it’s especially difficult for a guy like Frank Mir. Someone like Frank Mir has been to the highest of the highs. Then he got in a motorcycle accident and got that taken away from him. That man is so strong that he decided he was going to face his fear, step up and go back and do it again. So, he did it again.

“Then he runs into a brick wall and runs through, literally, murderer’s row inside the octagon, and it wasn’t very long ago when everyone inside the world of MMA said, ‘Hey, you’re down and out. It’s over. You should retire. You’re never going to be anything good inside of the cage.’ And the headlines were unbelievable. To be somebody that’s so great and to be a legend in MMA and have those things said about you, that’s very hard. It’s very easy to take a step back and to say, ‘I’m done. I’m not going to do this anymore.’ But Frank, we sat back, we talked and we said, ‘We need to find you, Frank. We need to find what you really want. Do you want to become the champion of the world again. Is this what you want?’”

Lundell said one doesn’t need to look far for visual representations of Mir’s excitement level in this new stage of his career.

“You can see it just in his approach to the octagon,” Lundell said. “He’s running out there. He’s excited to get in a fight. He’s excited to show who he is and what he’s capable of. Frank Mir has made gains that so many in mixed martial arts will never make, because it’s hard to become the best in the world and lose it, then become the best in the world and lose it and then to decide again at 36, ‘I’m going to be the best in the world.’ There’s not many out there that have that kind of will, that kind of strength, and that kind of tenacity. He has it.”

Check out the full conversation above.

And for complete coverage of UFC 191, check out the UFC Rumors section of the site.