“I’m the fittest I’ve ever been,” he said. “So I was ready to go the full 12 rounds. I’m full of energy now. What did it last? Under three minutes — my tank is totally full.”

Sadly, he never got the chance to go through the gears as Lemieux lived up to his reputation as one of the middleweight division’s most ferocious punchers.

O’Sullivan and his trainer Paschal Collins knew that, and had created a gameplan which involved soaking up early pressure, hoping to allow Lemieux to tire, before taking over the fight in the later rounds.

I was feeling comfortable, you know,” added Spike. “But when he hit me, that was all she wrote.

In all his years of boxing, not in competitive fights or behind closed doors in sparring, had O’Sullivan been knocked down. Even when he was outpointed by Billy Joe Saunders or forced into a seventh-round retirement by Chris Eubank Jr, Spike never touched the canvas.

That all changed on his Las Vegas debut, however, even if he didn’t feel it. He was in such distress that referee Russell Mora did not even bother to finish his count with the official time recorded at 2:44 of round one.

Spike said: “They say it’s the shots you don’t see coming that do the damage and it’s true.

“I didn’t even feel the shot land, it has never happened before, it’s a completely new experience.

I didn’t even know how long I’d been down for, I wondered whether it was minutes, he must have switched me off momentarily.

“I remember during our conference call he said he’d be the first to put me down and he was right about that. But fair play to him, he did what nobody else could do.

“My nose is broken but what’s new? I’ve done that 14 times already.”

After what was the 31st fight of his career, it was suggested that the 34-year-old father-of-four may decide to walk off into the sunset after banking a career-high purse understood to be around €300,000. In fact, aside from the main event fighters, Gennady Golovkin and Saul ‘Canelo’ Alvarez, nobody on the card earned more than him on Saturday night.

But O’Sullivan says he does not consider it a retirement fund as he plans to get back into the gym as early as this Saturday with a new schedule already mapped out.

His new-found sobriety, which continued even in defeat, meant he made the 11st 6lb middleweight limit very easily. He was only marginally above it on fight night while David Lemieux rehydrated to a staggering 179lbs (12 stone 7lbs).

So now Spike is plotting to drop down to the 11st light-middleweight limit and relaunch his career before the year is out.

He added: “I think I can certainly come back — really, I’m fucking disappointed with that punch. I genuinely thought I was going to win.

“Even though I lost I thought he was fairly sh1t to be honest, I thought he’d be better than he was.

“I thought ‘fucking hell this is going to be easy’ and probably got a bit too relaxed then next thing ‘bang’.

“Maybe the weight difference was a factor — hey, maybe it wasn’t. I know he was far bigger than me so the move down in weight makes sense.

“I made middleweight so easily this time because I’m off the booze. I didn’t need to cut at all and was eating plenty. I will be able to do 11 stone no problem.

“I believe the best is yet to come.”

First he will use his healthy pay cheque to move his family into a new home in Togher and briefly enjoy the money he has earned by way of his fists.

But that will not involve alcohol again. The cup of tea and a single bottle of alcohol-free beer which sits on the table in front of him in a busy Las Vegas bar is a testament to that.

“I was the third best paid on the card, only the main event fighters got more,” he said. “That makes me feel proud.

“I’m going to buy a nice house for my family when I get home. That’s why I do all this.

I went in the ring prepared to die for my family if I had to. I felt so good.

“Beforehand I signed a beneficiary form, like a will, a prior to the fight which guaranteed the money would be for her and my kids if anything bad happened to me. You never know, man.

“I went through some stuff in my life before when I thought I was going to die. I never thought I’d be around today but I’m still here, thankfully.

“I’m willing to die in the ring as long as my family are looked after — and that’s the truth.

“I’ve dealt with far worse in my time. It’s a boxing match. I’m sickened that I lost but life goes on.”

It is likely that his boxing life will continue under the banner of Golden Boy Promotions, who initially signed O’Sullivan up before he defeated Antoine Douglas in Montreal last year.

And the matchmaker who decided to pair Spike with Lemieux at the weekend says there is still a bright future for the moustachioed puncher.

Golden Boy’s Roberto Diaz said: “In most cases after an options package when you lose, that breaks the contract.“But in this particular case he got caught by one punch — he didn’t get beaten up. Anybody can get caught.

“When I made the match I thought it would be eight rounds of Hell because of their styles — but it wasn’t to be.

“It’s boxing. But Gary is a great fighter and he’s a promoter’s dream, now it’s just a matter of us bringing him back.”