It's hard to think of two competitors in the UFC who are as polar opposite as "The Notorious" Conor McGregor and Dustin "The Diamond" Poirier and the most obvious example can be found in the one man who unites them: "The Eagle" Khabib Nurmagodmeov.

Following his loss to Khabib in 2018, Conor immediately got into a brawl with Nurmagomedov's team and then didn't fight in the UFC again for two years; in the intermission, he repeatedly found himself in the headlines for bad reasons. When he did return last year at UFC 246, he steamrolled Donald "Cowboy" Cerrone at welterweight.

Following his loss to Khabib in 2019, Poirier and Nurmagomedov embraced, swapped shirts and later put them up for auction to raise funds for Poirier's Good Fight Foundation charity. Poirier was away from the UFC for nine months due to a hip injury. He spent that time training and preparing for his comeback, which came against fellow lightweight championship contender Dan "Hangman" Hooker. It was an all out war.

McGregor and Poirier faced each other before at UFC 178, and McGregor won with a Round 1 TKO. Typically such decisive victories don't engender rematches, but both men are so different now, one weight class, six years and 22 cumulative fights later, that their first contest was practically irrelevant — and that was proven as soon as the opening bell rang.

McGregor came out fast, pushed forward and hit Poirier with a stiff jab. The Irishman is known for having heavy hands (just ask Jose Aldo) but Poirier rolled with it. Since moving up from featherweight to lightweight, The Diamond has become significantly more resilient.

After trading hands for 30 seconds, Poirier got a takedown and forced McGregor towards the cage. This is the spot where Khabib excels so it was a smart tactic, or would have been were he as good a grappler as The Eagle. McGregor quickly wall-walked back to his feet and engaged in a clinch.

There wasn't much happening as Poirier had McGregor pinned against the cage but as Conor switched positions to the outside and Poirier kept his arms hooked, the tactic became clear. Poirier was holding on to McGregor to fatigue him rather than do any damage. In the final 90 seconds, when Conor escaped and the two men returned to the center of the Octagon, it looked like it had worked.

McGregor's punching was powerful, accurate and dangerous. It was also slower than usual and he was breathing deeply between combinations. The one knock against McGregor, even when he was on top of his game in 2015, is that he has poor cardio. He starts strong and tires quickly when against adversity; here, he was tired in under four minutes.

Not only that, he had no answer for Poirier's calf kicks. Every time he moved in, he clipped Conor's lead leg. Calf kicks are less powerful than standard leg kicks, however the precision behind them significantly limits the opponents' mobility.

Because of these, at the start of Round 2, Conor had a big welt on his right calf and was noticeably flat footed and trepidatious, even after nailing Poirier with powerful one-twos. McGregor has never been a versatile fighter and his limits became clear around the middle of this round; he began catching Poirier's leg as he went for the calf kick – and did nothing with it besides for push him back to the cage.

With 2:43 remaining in the second round, Poirier caught McGregor flush on the chin with a left straight. The Diamond was now in the position that Conor notoriously thrives in and began hammering in big, swinging hooks. McGregor stumbled away from the cage and began moving backwards, unguarded and Poirier laid him out flat. Referee Herb Dean jumped in conspicuously fast – did he learn from last week, when he let Calvin Kattar get pummeled for far too long, or did Dana White ask him to protect their top star? – preventing a full KO win for Poirier but the result was clear.

This is the first time Conor has lost by TKO and it calls a lot into question. Conor's biggest victories have come with his fists and he took two years out to box against Floyd Mayweather; he was even talking about fighting seven times in the next 18 months with one of those bouts being a boxing match versus Manny Pacquiao – and then he found himself viciously and undeniably outboxed by Dustin Poirier.

Post-fight, Conor spoke about being inactive and how that held him back. Georges St-Pierre was away from the sport for four years then came back and defeated then-UFC middleweight champion Michael Bisping in his first fight. The inactivity wasn't the problem, it was simply that Poirier is a better fighter and improved significantly since UFC 178, McGregor hasn't and he got exposed.