Replays showed his ankle rolling over as he stepped backwards seconds before the end of the round and the fight was stopped by doctors, handing Poirier a second straight win in their trilogy.
“This is not over,” McGregor said.
“If I have to take it outside, let’s take it outside,” he added as he was interviewed while sat on the canvas with his ankle strapped in a protective cast, before being taken out of the ring on a stretcher.
UFC president Dana White said after the fight that McGregor had broken the lower tibia in his left shin.
It meant the rivalry was perfectly poised heading into their trilogy bout in Las Vegas, and it was Poirier who emerged victorious in unfortunate circumstances.
The action started fast and furious as McGregor switched his tactics from the second fight and opened up with a succession of kicks.
But Poirier kept his cool and, after fending off McGregor’s early attacks, pushed forward with a flurry of punches before eventually forcing the action against the cage.
McGregor attempted to surprise Poirier with a guillotine choke, but the American stayed calm and escaped before punishing McGregor with heavy punches and elbows from top position.
And, when the fight returned to the feet, both men attempted to throw huge shots, with McGregor rolling his ankle when stumbling backward. Poirier then poured on the pressure in search of a finish, but the Irishman was saved by the buzzer.
However, it quickly became apparent that McGregor had suffered a serious injury, with replays showing the Irishman’s leg breaking as he stepped backward.
White hot atmosphere
The event was the first time the UFC had played to a full crowd in its home town since UFC 248 in March 2020, as a capacity crowd packed the 20,000-seat T-Mobile Arena in Las Vegas to watch Poirier and McGregor complete their trilogy.
The level of anticipation was down in large part to an ill-tempered fight week that saw McGregor turn up the heat on Poirier in an attempt to get under the Louisiana man’s skin as the fight drew closer.
While the build-up to their second bout at UFC 257 was remarkably cordial, tensions were sky high ahead of the trilogy bout, with McGregor issuing a chilling warning to his opponent ahead of fight night, declaring, “I’m gonna make this man pay with his life. And I mean it!” after the pair faced off at the ceremonial weigh-ins on Friday.
It meant the atmosphere inside the arena was electric by the time both men made their walk to the octagon.
And tensions were still high at the conclusion of the bout, with Poirier suggesting a checked leg kick caused the initial injury to McGregor and his stumble later in the round exacerbating the injury and forcing the stoppage.
“He fractured it in one of the checks at the beginning of the fight and he broke it on a punch, for sure. I felt something, he was kicking me hard,” he said.
“There’s no coming back from that,” the American added. “He was saying he was going to murder me, that I’d leave here in a coffin. You don’t talk like that about people. I hope he gets home safe to his beautiful family.”
McGregor angrily refuted that assessment as he vowed the rivalry between the pair was far from over.
‘McGregor can’t end his legacy on this’
Nick Peet, MMA journalist: “Conor McGregor can’t end his legacy on this, a freak injury. It won’t sit right with him.
“Let’s not get away from the fact we got one round of action, and that was categorically won by Dustin Poirier.
“You wanted a conclusive finish so the trilogy could end but now the trilogy hasn’t ended, in my opinion.
“We’ve got to see something else. To end it here doesn’t sit right with me. I don’t think Poirier-McGregor is done.”
“There’s definitely unfinished business. McGregor’s a fighter first. Despite everything else he’s got going on, he’ll always want to fight.
“He’s not going to want to go out like this, to let this be the end. He’s going to come back and there’s many options for him.”