Dustin Poirier has won UFC 264 by TKO after Conor McGregor suffered a nasty leg injury at the end of the first round on Saturday in Las Vegas.

American Poirier was firmly in control, dominating the early exchanges, before McGregor attempted a punch and fell on his own left leg causing an apparent fracture and a doctor's stoppage.

McGregor left the octagon with a leg splint on in a stretcher, casting doubts on his future in the sport.

"He fractured in one of the checks at the beginning of the fight," Poirier said after the fight. "Then it broke on a punch, for sure.

"When I pointed at him at the beginning of the fight, that's when I checked a good kick and I felt a crack. it was probably cracked and then on the twist of the punch it finished."

Despite the defeat and being unable to stand, the Irishman continued to trash talk Poirier as he had in the lead-up to the fight when he said he would "murder" the American.

Poirier added: "There's no holds barred with the trash talk but murder is something you don't clown around with.

"This guy was saying 'he was going to murder me, I was going to leave her in a coffin'. You don’t talk to people like that. I hope this guy gets home safe to his beautiful family."

He added: "This guy's a dirtbag… Karma's not a b****, she's a mirror and this guy's said the wrong s*** and I've been busting my ass."

Poirier had no doubt he deserved the win despite the circumstances of the victory, in the latest edition of their trilogy.

"Sometimes these things happen. I beat the guy," he said.

Poirier becomes the eighth fighter in UFC history to earn 20 wins.