John McCarthy was on the mats back in July, teaching Brazilian jiu-jitsu like he had done probably thousands of times before.

The legendary MMA referee and BJJ black belt was demonstrating how to put on a proper d’arce choke, so he got down on the ground and had the student put one on him. McCarthy was in it for about 90 seconds until the student had the proper technique and then he tapped out. The well-known figure affectionally nicknamed “Big John” got up and went about his day. He was totally fine.

The next morning, something was horribly wrong. McCarthy had a burning sensation shooting down from his neck and shoulders into his arms. He had no feeling in his thumbs. McCarthy compared it to a stinger that football and hockey players get, except this one would not go away. It was constant.

“I hurt my neck really bad,” McCarthy told Ariel Helwani on Monday’s edition of The MMA Hour. “I actually got paralyzed on one side of my body.”

McCarthy said he has had neck troubles in the past. This time, he said he “destroyed” the C5, C6 and C7 vertebra. The discs were broken apart and pinching down, crushing nerves. McCarthy went in for surgery in August, but the pain and burning continued.

“The [nerves] that were leading into my arms just were crushed,” McCarthy said. “My thumbs were completely numb, my fingers were numb. I had that burn coming down from my shoulders.

“It just was a serious problem.”

McCarthy had another surgery in September. The vertebra were fused, he said, and spacers were put in to protect the nerves. He said now he feels “great,” but he understands that he cannot do the same things he used to do, including a lot of rolling jiu-jitsu and technique as a referee in the cage.

“I’m not the same person,” McCarthy said. “I used to be able to do things, I could grab someone and pick them up. Those days are gone for me. … It taught me a lesson and it made me realize how fast I can absolutely lose what I love doing.”

McCarthy, 55, took a break from refereeing all summer into the fall and returned for UFC 217 in November to officiate the middleweight title fight between Georges St-Pierre and Michael Bisping. In the back of his mind, he was already thinking about the future.

Then, just a few days after refereeing at UFC 219 on Dec. 30, McCarthy got a call from Bellator president Scott Coker. Bellator had just parted ways with longtime color commentator Jimmy Smith. Coker asked McCarthy if he wanted to audition for that role. McCarthy jumped on it — and he got it. He’ll make his Bellator broadcasting debut at Bellator 192 on Saturday in Los Angeles.

“You gotta take chances in this world,” McCarthy said. “There was no place for me to go in the officiating world. I mean, I loved what I did. But I didn’t want to be the guy that hung on too long and I didn’t want to fall. I didn’t want to start going down and I didn’t want someone telling me, ‘Man, you need to get out, you’re not doing things right.’ It was a chance for me to get out on my own terms.”

McCarthy won’t say he’s retiring from refereeing, but for the time being he won’t be officiating any high-level MMA fights. However, he is still licensed as a boxing referee and judge in California and a boxing judge in Nevada, so he’ll be carrying on his work in regulation.

“Big John” said he’ll “treasure” the 24 years he spent refereeing UFC fights, going back to UFC 2 in 1994. The retired Los Angeles Police Department officer said that the last few months, including the bad injury, have led him down this path and he’s excitedly preparing for his second go at the broadcast booth. McCarthy briefly worked for The Fight Network and Affliction about a decade ago.

“Somebody is telling me something,” McCarthy said. “That’s really why this whole move came about.”