Let's Talk About Conor McGregor's Achilles' Heel

Mark J. Rebilas-USA TODAY Sports

When it was over, Floyd Mayweather Jr. admitted that his plan all along was to let Conor McGregor punch himself out.

Mayweather had just scored a 10th-round TKO victory over McGregor in last Saturday's much-hyped junior middleweight boxing match at T-Mobile Arena in Las Vegas. Fielding a post-fight question from Showtime Sports interviewer Jim Gray, the veteran pugilist explained why he'd started the bout so slowly and allowed McGregor to build an early lead before roaring back for the finish.

"Our game plan was to take our time, let him shoot all his heavy shots early on and then take him down at the end, down the stretch," Mayweather said. "We know in MMA he fights 25 minutes real hard and after that he starts to slow down."

If this was indeed Mayweather's strategy, it was an effective one.

It was also well-informed.

Those familiar with McGregor's body of work as a two-division UFC champion already knew the swaggering Irishman's one Achilles' heel—aside from perhaps his submission defense—could be his endurance.

McGregor hands out on the ropes as referee Robert Byrd moves Mayweather back.Joe Camporeale-USA TODAY Sports

If you count Saturday's match against Mayweather, McGregor is now 11 fights into his run on the worldwide stage. He's fought in two different sports, four total weight classes and against a very disparate group of opponents. All told, the results have been overwhelmingly positive. McGregor is 9-2 since 2013 (again, counting Mayweather), has won titles in two weight classes and set box office records in both MMA and boxing.

On the rare occasions things go wrong for him, however, there appears to be one constant: McGregor gets tired.

After both of the fighter's high-profile losses—first to Nate Diaz at UFC 196 in March 2016, then to Mayweather—McGregor has at least partially blamed his own gas tank.

Case in point: Following Saturday's referee stoppage, the 29-year-old Dublin native steadfastly maintained that Mayweather never really hurt him. The real problem, McGregor insisted during his own interview with Gray, was that he got too winded.

"I was just a little fatigued," he said. "I get a little wobbly when I'm tired. It is fatigue. The referee could have let it keep going, let the man put me down. I am clear-headed. Where were the final two rounds? Let me wobble to the corner and make him put me down."

On Thursday, McGregor essentially doubled-down on that assertion. He detailed his training for the fight in a lengthy Instagram post, going so far as to say he might have won if he'd made a couple of minor tweaks to his preparations:

Of course, there are a lot of other perfectly good—and arguably unavoidable—reasons why McGregor might have slowed down against Mayweather.

Boxing provides a different cardiovascular challenge than MMA, and by the time Mayweather ended their fight with strikes, the two had been battling for just over 28 total minutes. That made it the longest bout of McGregor's career.

Both fighters also had relatively short training camps between the bout's announcement in June and fight night. Factor in the otherworldly level of competition McGregor faced in his first boxing match, the magnitude of the event itself and Mayweather's consistent work to the body during the fight and perhaps anyone would've been fatigued by the end.

Then again, we've seen endurance be a factor in McGregor's MMA bouts as well.

In the wake of that second-round submission loss to Diaz, McGregor told the UFC's Megan Olivi he'd been "inefficient" with his energy. He also promised to go back to the training room and figure out how to solve the problem.

"I lost in there," McGregor said. "There were errors, but errors can be fixed if you face them head on."

A bit more than five-and-a-half months later, he and Diaz rematched at UFC 202 and it was obvious McGregor had indeed taken steps to address the issue. He was noticeably more reserved during his walk to the cage and introductions and appeared more deliberate once the fight started.

He began by feeding Diaz a steady diet of low kicks to supplement his normal left-handed power punching. The strategy seemed to work early on, as McGregor dropped Diaz to the canvas with strikes three times during the fight's first seven minutes. As the second round wore on, however, McGregor began to lag—just as he had in their first fight.

The third round was a borderline 10-8 win by Diaz. Though McGregor rebounded during the championship fourth and fifth frames and ultimately squeaked by with a majority decision victory, a profile of him began to emerge.

Perhaps McGregor is a competitor who comes out of his corner fast but fades the longer his fights go on.

Mayweather clearly knew this headed into their boxing match and used it to his advantage.

McGregor knows it too, but implied during a post-fight interview with ESPN.com's Brett Okamoto that the situation is under control. He also noted he thinks it may be more a psychological problem than physical.

"I don't know what it is; it's a mental thing or something," McGregor said. "It happened in the Diaz 2 fight as well. I had a little stage at the end of the second round and end of the third, but then look what happened in the fourth and then the fifth—I came back. I overcame it."

In fairness, he has a point.

So far, McGregor's endurance hasn't exactly derailed his rise. He did win the second fight against Diaz, after all, and in his only other UFC fight to go the distance—a three-rounder against a very green Max Holloway in August 2013—he didn't appear to suffer from fatigue at all.

More often than not, McGregor has ended his fights so quickly that he hasn't had to test his energy reserves. Of his 21 professional MMA wins, 19 have been first- or second-round stoppages.

It's not at all unusual for MMA fighters to struggle with their cardio, either. The sport is so grueling that even top professionals are spent after 15-25 minutes of competition. For someone who typically starts as fast and throws as hard as McGregor does, there are bound to be hurdles.

McGregor reacts to referee Robert Byrd's stoppage.Mark J. Rebilas-USA TODAY Sports

Still, McGregor's conditioning issues appear more obvious than most—maybe because he's been so good in every other aspect of the fight game. It's striking to watch a guy who is otherwise so mentally and physically sound consistently encounter the same problem.

It's also an awkward look for someone who spent much of the lead-up to the Mayweather bout hocking his new for-purchase "McGregor Fast" conditioning program.

McGregor is so meticulous and calculated that it's hard to believe he'll let such an obvious flaw hang around for long.

But if Mayweather knew the correct strategy was to weather McGregor’s early storm and start to pressure him later in the fight, McGregor’s future MMA opponents will know it, too.

The blueprint of how to beat him is out there now. You can bet guys like Diaz, Tony Ferguson, Kevin Lee and Khabib Nurmagomedov all took note.

But if McGregor's biggest weakness to this point has been his endurance, one of his biggest strengths has been his analytical nature.

As he moves forward, he'll know he needs to adapt and close the holes in his game.

The fun part will be seeing how he responds.