McGregor's defeat on Saturday night was the first time that he'd been beaten by TKO in MMA, with his previous four losses all coming by submission.
It was an incredible performance by Poirier, who finished the fight half way through the second round with a flurry of punches that floored his opponent and left him unable to defend himself.
Whilst it was Poirier's hands that ended it all, it was the Diamond's leg kicks that started the onslaught, with McGregor unable to put weight on his right leg without it buckling.
Now one doctor has explained exactly what impact the strikes had on the Irishman. Physician Brian Sutterer explains sports injuries on his YouTube channel and McGregor's leg injury is the subject of his latest video.
"As soon as he put weight on that right leg, he was in some serious discomfort," the doctor explained.
"[Poirier's leg kicks] made contact exactly on this kind of lateral aspect of McGregor's lower leg near the outside of the calf. Even right away we can see McGregor have some pain here, having difficulty putting weight on that leg. And that just accumulated throughout the fight, so at the end, McGregor's leg was basically dead."
"A kick in this area is specifically targeting something we call the common fibular nerve...it's the nerve that supplies muscle control to part of the lower leg, but also some of the sensation.
"Pay attention to exactly where Poirier's leg is making contact with McGregor's, it's just below his knee.
"This is where these UFC fighters are trying to strike to have these effective calf kicks. The green nerve [in the video] is that common fibular nerve, and what's important about it is how superficial it is, meaning how close it is to the skin.
"A lot of other big nerves in our body are deep beneath skin or deep beneath muscle, and so they're pretty well protected. But this nerve in particular is really close to the surface and really susceptible to these stuns and getting injured."
Despite Poirier 'killing' McGregor's leg, with the former two weight champion repeating that his leg was 'dead' on several occasions, things remained quite jovial between the pair.
Someone caught a video of the pair meeting backstage around the time of their press conferences with the Irishman jokingly saying 'you broke my leg, you b****rd' as he hobbled past.
McGregor might be limping for a while more by the looks of it.
Featured Image Credit: YouTube
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