In the end, Michael McDonald’s biggest rival was his own body.

A world-class bantamweight who competed for both Bellator and the UFC, McDonald announced his retirement from mixed martial arts last week at the age of 27, electing to hang up his gloves less than two months after his spectacular 53-second knockout of former Bellator champion Eduardo Dantas.

McDonald was a contender in the 135-pound division from an early age, even challenging for the UFC bantamweight title in 2013, however repeated hand injuries plagued him throughout the final five years of his career, and he was left with a difficult decision to make after he badly re-injured his left hand in his Bellator 202 win over Dantas this past July.

McDonald characterized the injury as one that left him in the most excruciating pain of his life. Reflecting on his recent road on Monday’s episode of The MMA Hour, McDonald said he had to be rushed to the emergency room as soon as he arrived home in California following Bellator 202. He said the swelling in his left hand was so bad that he nearly needed emergency surgery to avoid doctors amputating the hand. Fortunately, the hand surgery ended up being a success, however the procedure left McDonald still dealing with a rare and debilitating side effect in his left arm that he never expected.

“I have zero function of my left bicep whatsoever,” McDonald said Monday on The MMA Hour. “There was an issue during the surgery, and we think it was the anesthesiologist, not the surgeon that I had, that I actually have zero ability to use my left bicep whatsoever. It’s completely dead. So, already my left arm is like half the size of my right arm. Now it’s been almost a month that I have not been able to use my left bicep whatsoever, so I can’t open a jar, I can’t get a box out of the cupboard, I lift a sheet of plywood or a cabinet. Nothing.

“I talked to my surgeon about it and he used a lot of big words and told me a lot about it. He said, ‘The way that this happened, it’s still connected, but basically it’s not coming back, it’s not waking back up.’ Now, there are different reasons that people’s muscles don’t come back after surgery, but this particular reason and how this happened is about a 1-in-8,000 chance. My surgeon is a surgeon of 20 years and he said he’s never seen it happen to any of his patients, so it’s quite a rare thing when it happened.

“The good news is all recorded cases have recovered that have been recorded in a medical journal. Its not a for-sure thing that it comes back, but the odds are in my favor that it does. But just because it comes back doesn’t mean it’s not a huge burden on my life. They said on average it can take up to six months to come back, so literally not being able to use your arm for six months, that kinda sucks.”

For McDonald, his latest health complication was a clear enough message to retire.

A devout Christian, McDonald said he prayed on the question of whether he should continue fighting prior to his bout against Dantas, asking God to send him a sign about whether it was time to move on to the next chapter of his life. The repeated injuries had hampered his both health and his livelihood, and McDonald said he was starting to wonder if he was keeping my priorities in order going down the path he was on.

And for McDonald, the answer he received at Bellator 202 couldn’t have been more clear.

“Part of that prayer was me saying, ‘God, I don’t want any what-ifs.’ I don’t want any, ‘Oh man, what if I kept going?’ And, ‘Oh man, should I really be doing this now?’ God said that he is not a god of confusion, so make me sure,” McDonald said. “Make me have zero confusion. Let me be sure, and if you make me be absolutely positive, then I will change my path and I will relentlessly pursue it, just like how you commanded me to pursue my fighting career to the best of my abilities. So he made it 100-percent clear that I’m supposed to be moving on and that the price outweighs the reward at this time with fighting, both for me personally, for my life, just everything about it.”

Along with being an MMA fighter, McDonald has doubled as a professional woodworker for many years. He currently runs a custom woodworking business that specializes in cabinets, furniture, and cutting boards — Mayday’s Custom Woodworks — and McDonald admitted that his current predicament with his left arm is affecting that aspect of his life as well.

“This is my fifth hand surgery in five years, and like I said, not only that, I almost lost my hand,” McDonald said. “I have possible permanent damage, and after the surgery, I am not joking, this was the absolute worst pain of my entire life. It would not stop. It was like someone took one of my Jet parallel clamps that I use in my woodshop and just freakin’ clamped it down to 10. It was excruciating to the point where I didn’t think it could get any worse. I was like, ‘Okay, this is a 10. This is the most pain that anyone could possibly feel,’ and I’m like, ‘I can’t get worse.’ And it got worse, 10 times over; it just got worse and worse and worse over eight hours, to the point where I was just pushed to exhaustion at the most excruciating pain I’ve ever been in in my life, of just pushed to tears.

“I was just so exhausted of feeling that pain. After these experiences, I would never want to even put myself in a situation where I have to do this again. Hard pass.”

McDonald now walks away from mixed martial arts with a professional record of 19-4.

He began his UFC career with an unbeaten four-fight run from 2011-12 which culminated in a breathtaking first-round knockout of Miguel Torres. That win catapulted McDonald into an interim 135-pound title bout against eventual UFC champion Renan Barao, which he lost via fourth-round submission. “Mayday” then left the UFC in 2016 for Bellator MMA, where he went 2-0 with a decision win over Peter Ligier and his highlight-reel knockout of Dantas — a performance that ended up marking the final fight of McDonald’s career.

“I have no regrets,” McDonald said. “Even the losses, I learned so much from my losses. I learned so much about masculinity, about being an adult, just about success, through these losses, even more so than the wins. So I think it was an incredible learning experience. God really showed it to me that, it’s like college. I was fighting 13 years. Someone goes and gets a PhD for 12 years — that’s basically what I did. I got a PhD in success, in hard work. I have a great community of people around me now, and I’m equipped to do my next thing with zero debt, so that’s kinda how God showed me this period of my life was kinda like college.”

Asked for his favorite memory from his time in the sport, McDonald says there are many moments that stand out, but one in particular that stands above all of the rest.

“I have some good ones, but definitely, without question, my favorite MMA memory was after my fight with Alex Soto [in 2011], I got a message from a girl. And it turned out that I married her, so that was pretty cool,” McDonald said.

“My wife’s father, so now my father-in-law, it’s my coach’s best friend, and we never met. She’s a lifelong martial artist, she’s been doing martial arts since she was 2, she outranks me in martial arts, but we never met though. And she came to my fight to support my coach, and then after that she sent me a message on Facebook, congratulated me, and I learned that not only is she a dancer, but she’s also a very attractive martial artist, so I started flirting with her, took her out on a date, and here we are.”