GLENDALE, Ariz. — Dustin Poirier hobbled in on crutches after way-too-many kicks made it tough to bend his right leg. He had stitches in his face, may have broken his left hand.

Poirier knew his fight with Justin Gaethje would be like this. He survived and won with a big left hand, moving a step closer to his title shot.

Poirier stunned Gaethje with a hard left hand in the fourth round and won by technical knockout in brutal a UFC lightweight fight among top contenders Saturday night.

The fifth-ranked lightweight, Poirier (23-5) bloodied Gaethje in the first round and finished him off with a flurry early in the fourth, yelling "I'm going to get that title fight this year!" as he left the octagon.

"As I thought about the possibilities this fight could take, I knew I would have to dig down deep, I knew trouble would present itself," Poirier said. "I just stayed tough and believed in myself, got it done.

Gaethje (18-2), from Safford, Arizona, had the crowd support and landed a series of punches in the second round after a shaky first. He won the third round on all three scorer's cards despite a point deduction, but couldn't avoid Poirier's left hand in the fourth to lose his second straight fight after opening 18-0.

"I'm content with what just happened, as crazy and as stupid as that sounds," said Gaethje, the No. 6 lightweight. "I don't fight to win or lose. I fight to entertain people. This is entertainment business and I fight for money."

Alex Oliveira filled in as a replacement against Carlos Condit in the co-main event after Matt Brown tore his ACL. The 30-year-old Brazilian earned the biggest win of his career in the desert on two weeks' notice, forcing the former interim welterweight champ to submit with a second-round guillotine choke hold in a fight that bloodied both fighters.

"I fought on short notice and gave a show," Oliveira said through a translator. "I was training, I knew I could be called at short notice. I'm a UFC employee and I know I have to be ready when it comes."

Gaethje earned the nickname "The Highlight" for his hyper aggressive style, but Poirier took the fight to him. Poirier hit Gaethje with a couple of combinations, bloodying the left side of his face midway through the first round while dodging most of Gaethje's counter attempts.

Gaethje started landing punches in the second round and wore Poirier down with a series of hard leg kicks, revving up chants of "Gaethje!" from the crowd.

Gaethje staggered Poirier with a hard right early in the third round, but was deducted a point late by referee Herb Dean for hitting with an open hand the second time in the fight.

"I didn't see the shot — I think it hit me somewhere on the left side — and I backed myself up against the cage, which is something I don't want to do with a guy like that, especially when they hurt you," Poirier said. "But I felt like I got my wheels under me pretty quick."

Poirier was still ahead on all three cards and left no doubt in the fourth round, stunning Gaethje with the left hand and burying him in a flurry of punches until Dean stepped in to stop it.

Up and comer middleweight Israel Adesanya of New Zealand won a split decision over Italian Marvin Vettori. Michelle Waterson opened the main card with a split-decision victory over Cortney Casey in a technical straw weight fight.