McGregor suffered a TKO defeat to Poirier last weekend and has claimed he had a stress fracture going into the fight.
The Irishman then broke his left leg towards the end of the first round - but NAC's executive director Bob Bennett had no idea about the injury.
Without directly referencing McGregor, Bennett said per MMA Junkie: "If we ever knowingly had information a fighter wasn't fit to fight, we wouldn't let them compete.
"It would go to a doctor, and a doctor would make that decision as the expert."
McGregor went into surgery on Sunday and was released on Wednesday, which was his 33rd birthday.
In a video posted to Instagram, the former 'Champ-champ' spent six minutes breaking down his condition while driving on a scooter.
He said: "I was injured going into the fight. People are asking me, 'at what point did the leg break?'
"Ask Dana White, ask the UFC, ask Dr Davidson the head doctor of the UFC, they knew my leg had a stress fracture going into that.
"They were debating pulling the thing because I was sparring with no shin pads, and I kicked a knee a few times.
"I had multiple stress fractures in the shin bone above the ankle. And then I have trouble in my ankle anyways throughout the years through fighting all the time."
McGregor then insisted his strategy inside the T-Mobile Arena backs up his claims he was carrying an injury.
"Also, I was wrapping my ankle every training session. When the ankle was sore, I still wouldn't stop training - I used to just train on my back.
"And that's how I developed those ground shots from the back, that's why Dustin backed away when he was on top of me. And I was landing the up-kicks and the elbows, it's a horrible place to be in.
"It was a skill I developed because I'd the damaged leg and had to adapt my training... I needed to get treatment on the ankle and shin-bone, and I would never have committed to going under the knife unless something like this happened."
McGregor won't be back in the Octagon until 2022 and has been handed a medical suspension until January 7.
UFC president Dana White has said a fourth fight between McGregor and Poirier is entirely possible.
Poirier is likely to challenge lightweight champion Charles Oliveira down the line.
Featured Image Credit: PA Images & Conor McGregor/Instagram
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