One of the most remarkable runs in UFC history continues, but it was much more difficult than expected.

Alex Pereira methodically broke down a game Khalil Rountree Jr. and used a bruising sequence of body punches to retain his light heavyweight championship with a fourth-round stoppage Saturday night in the main event of UFC 307 at the Delta Center in Salt Lake City.

Pereira (12-2 MMA, 9-1 UFC) was slotted into his third title defense in 176 days after headlining UFC 300 in April and UFC 303 in June. Unlike his knockout victories against Jamahal Hill and JiYí Procházka, Pereira faced adversity against an opponent who refused to go away willingly.

Rountree was up on all three of the judges' scorecards, 29-28, heading into the fourth.

"This was one of my toughest fights. I expected that," Pereira said. "The game plan was to let him tire. I saw he started decreasing his stamina in the second round. My stamina only goes up."

Fighting out of Las Vegas, Rountree Jr. (14-6 MMA, 9-6 UFC) drew heavy criticism for being selected to challenge for the 205-pound title as the UFC's No. 8-ranked light heavyweight, with No. 2-ranked Magomed Ankalaev being surprisingly passed over. But Rountree proved his worth by withstanding an immense amount of punishment and getting the better of the striking exchanges in the early rounds.

"Poatan" was disciplined from the outset, feeding the challenger a steady diet of calf kicks and jabs. Rountree was undeterred in the opening rounds and connected with several left hands to get the champion's respect.

In the second round, Rountree briefly dropped Pereira to a knee by countering a head kick with a right hand. Pereira wasn't hurt, but it was clear that Rountree could match him in the power department. As the fight wore on, Pereira patiently snapped the jab and deployed the calf kick. By Round 3, Rountree's base was compromised and the altitude in Salt Lake City began to take a toll on his conditioning. In the final minute of the round, Rountree was gasping for air as Pereira rolled forward and blasted the challenger with punches that opened up several cuts around the eye.

Sensing that Rountree was fading, Pereira spent the early minutes of the fourth round allowing the challenger to exhaust what was left of his gas tank. Pereira calmly pressed forward and rocked Rountree with a right hand. The challenger went into survival mode and swung for the fences in hopes of catching Pereira with his power. But "Poatan" was both poised and relentless with his assault, bouncing a series of violent punches off of Rountree's face as the challenger staggered around the Octagon.

In a violent finishing salvo, Pereira snuck in an uppercut and unleashed a wicked body combination that took what was left of Rountree's resolve. The challenger sank to the canvas at the 4:32 mark as Pereira collected his third successful title defense.

Pereira outlanded Rountree 63-15 in significant strikes in the fourth round, and had a 127-61 edge for the fight.

Pereira joined Jon Jones, Anderson Silva, Chuck Liddell and Frank Shamrock as the fifth fighter to win three PPV main events in a calendar year by knockout or submission.

The remarkable run of Pereira over the past year has left many wondering where he will go next. Pereira has teased the possibility of moving back down to middleweight to challenge champion Dricus Du Plessis or climbing up to heavyweight for a blockbuster showdown with current champion Jon Jones.

But "Poatan" appears to be comfortable right where he's at.

"We saw that Dricus was fighting Sean Strickland next," Pereira said. "He's a training partner and I don't want to get in the way. I can move up to heavyweight, but this division is great and this is where I'm at."

Whatever he decides to do next, the world will be watching as the legend of "Poatan" continues to grow.