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

Alex Pereira broke Khalil Rountree Jr. methodically finished a match, using a series of heavy 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 making his third title defense in 176 days after headlining UFC 300 in April and UFC 303 in June. In contrast to his knockout victories against Jamahal Hill and JiYí Procházka, Pereira faced adversity against an opponent who refused to leave voluntarily.

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

“This was one of my toughest fights. I expected that,” Pereira said. “The plan was to let him get tired. I saw that in the second round he started to lose his stamina. My stamina is only going up.”

Rountree Jr. (14-6 MMA, 9-6 UFC) fought out of Las Vegas and was heavily criticized for being selected to fight for the 205-pound title as the UFC’s No. 8 light heavyweight list, with No. 2-ranked that Magomed Ankalaev was surprisingly passed over. But Rountree proved his worth by enduring a tremendous amount of punishment and gaining the upper hand in the striking exchanges in the early rounds.

“Poatan” was disciplined from the start, feeding the challenger a steady diet of calf kicks and punches. Rountree was undeterred in the opening rounds, connecting with several left hands to gain the champion’s respect.

In the second round, Rountree briefly dropped Pereira to one knee by countering a head kick with a right hand. Pereira was not injured, but it was clear that Rountree could match him in terms of energy. As the fight progressed, Pereira patiently snapped the jab and used the calf kick. On lap 3, Rountree’s base was in jeopardy and the altitude in Salt Lake City began to take its toll on his fitness. In the final minute of the round, Rountree gasped for air as Pereira rolled forward and peppered the challenger with punches that opened several cuts around the eye.

Sensing that Rountree was fading, Pereira spent the opening minutes of the fourth round allowing the challenger to deplete the rest of his gas tank. Pereira calmly pressed forward and rocked Rountree with his right hand. The challenger went into survival mode and swung for the fences hoping to catch Pereira with his power. But “Poatan” was both poised and ruthless in his attack, bouncing a series of violent punches onto Rountree’s face as the challenger staggered around the Octagon.

In a violent final volley, Pereira sneaked in an uppercut and unleashed a vicious body combination that took over what remained of Rountree’s resolve. The challenger sank to the canvas at 4:32 as Pereira collected his third successful title defense.

Pereira defeated Rountree 63-15 with significant striking in the fourth round, and had a 127-61 lead 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.

Pereira’s remarkable performance 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 moving up to heavyweight for a blockbuster showdown with current champion Jon Jones.

But “Poatan” seems comfortable where he is.

“We then saw Dricus fighting Sean Strickland,” Pereira said. “He’s a training partner and I don’t want to get in his way. I can move up to heavyweight, but this division is great and this is where I am now.”

Whatever he decides to do, the world will watch as the legend of “Poatan” continues to grow.