Sergei Pavlovich was a terrific athlete growing up in Russia. He played a lot of basketball, dabbled in handball and in wrestling. But the one thing that was pretty certain from a young age is that he was going to fight. His environment almost demanded it.

He grew up in the Southern Russian city of Rostov-on-Don, where it was just a given that boys were going to have to fight.

He didn't have to wrestle bears, like UFC Hall of Famer Khabib Nurmagomedov's late father, Abdulmanap, had Khabib do growing up in Dagestan, but Pavlovich was in his fair share of scraps as a kid.

"We grew up in the kind of place where you constantly had to fight for yourself, fight for your rights," Pavlovich told Yahoo Sports. "You had to be able to be strong. You had to be a strong person in order to survive there. So fighting was pretty much in my soul and in my spirit when I was growing up."

He's just as menacing as an adult as he had to have been to his peers growing up in Rostov-on-Don. He's 6-foot-3, weighs 260 pounds and has inexorably positioned himself at the top of the UFC's heavyweight rankings. On Saturday in the co-main event of UFC 295 at Madison Square Garden in New York, Pavlovich will face Tom Aspinall for the interim heavyweight championship, after the fight between champion Jon Jones and former champ Stipe Miocic fell out due to a Jones shoulder injury.

Pavlovich was preparing to be the Jones-Miocic backup, but it was no shock when he got the news he'd be fighting Aspinall. The two had been eyeing each other for a while and were scheduled to fight each other twice, though neither one happened.

But they are remarkably similar. Pavlovich is 31 years old with an 18-1 record and 15 knockouts. Aspinall is 30 years old with a 13-3 record and 10 knockouts. Aspinall is 6-5, so a bit taller than Pavlovich, though Pavlovich has an 84-to-78-inch advantage in reach. Both weigh in right around 260.

In the UFC, they are even more similar. Both are 6-1 in the promotion. Aspinall's only UFC loss came 15 seconds into the first round of a fight with Curtis Blaydes, when he seriously injured a knee. Pavlovich's only UFC loss was in his debut when he was stopped by Alistair Overeem in the first.

But other than the loss to Blaydes, Aspinall is 6-0 in the UFC with four first-round knockouts, a first-round submission and a second-round submission. Pavlovich is 6-0 after losing to Overeem and has won all six by knockout in the first.

"I always knew that we'd eventually meet [in a big fight]," Pavlovich said. "Of course, I wasn't expecting it when I [agreed to be the backup for Jones and Miocic], but I knew it was going to occur at some point and I think Tom would say the same thing."

He did, in fact, say the same thing. And it's one of those fights that is sure to have the crowd on its feet from the get-go.

Aspinall has the shortest average fight time in the UFC at two minutes, 19 seconds. Pavlovich has the third-shortest average fighting time at 2:23. Drew McFedries is No. 2 with an average of 2:20.

Pavlovich has torn through his opposition since the loss to Overeem. He said he learned more from that fight than any other but was reluctant to talk much about it. He didn't want to come off like he was making an excuse, but the fight was in Beijing and said he didn't arrive nearly early enough.

"Please understand, in no way am I trying to make an excuse for this loss, and I understand a loss is a loss," he said. "I have taken it as a man. But the fact is, and I've said this before, that I only came into China four days before the fight and on the day of the fight, I was still dealing with some pretty serious jet lag.

"I learned from that. Part of being a professional is knowing those things, and I learned how important it is when I fight in a different time zone for me to arrive with enough time to recover so that I can be at my best. And so that's something that I've done since, and it's why I say I learned so much from that fight."

While Pavlovich may be the better pure striker, Aspinall likely is better on the ground. But Pavlovich trained at the American Kickboxing Academy in San Jose, California, for a while, and two of the heavyweights he used to roll with were former UFC champions: Cain Velasquez and Daniel Cormier.

It's been five years since he's been at AKA, he said, but he conceded he did learn a lesson from them.

Given their records, it's probably going to be a short night either way. Pavlovich insisted he's not thinking that way and is prepared for any eventuality.

But when you have a pair of heavyweights with a combined record of 31-4 and 28 finishes, the odds are long it's going to see the fifth round. For Pavlovich, there is only one thing on his mind.

"The UFC belt," he said."That's all that matters, getting that belt."