“People might laugh at me but I couldn’t give a f**k,” he explains. “I write it down every night: ‘I will be the unified middleweight champion of the world’.
“The universe is taking care of things and it’s aligning the people. I have no idea how I got here really.”
Here, for this weekend at least, is Montreal where O’Sullivan has landed the prime, co-feature slot on Billy Joe Saunders’ world middleweight title defence against local favourite David Lemieux tonight.
The 33-year-old takes on Antoine Douglas, one of the rising stars of American boxing, but is driven by the suggestion that victory here could set up his first world title challenge in his very next fight.
It is a far cry from this time two years ago when Spike, who leaves his family in Cork to live in Dublin from Monday to Friday, came close to quitting the sport altogether after he was stopped by Chris Eubank Junior in London in December 2015.
“I got my eardrum burst against Eubank and after that fight I was going to quit,” he said.
“I trained for about 20 weeks for that fight, it was the longest camp of my life. I scheduled a holiday with my family a week after that fight and we flew to Lanzarote. When the plane was descending my ear went and when I got off the plane I could hear nothing.
“I said, right that’s it, I’m going to jack it in. “I thought it was a serious problem, a weakness there because it was the third time my eardrum had burst.
“But I saw a top specialist and he insisted it was fine, the injuries were just very bad luck so I decided to continue.”
He has been rebuilding steadily since that defeat and three victories already in 2017 has launched him into a potentially life-changing bout here in Montreal, where the temperatures are 20 degrees. Should he make it four out of four for the year, O’Sullivan’s first bout of 2018 could be his dream world middleweight title shot.
“Golden Boy are backing me here,” he added.
“I have signed a four-fight deal with them and they have told me their plans.
“They told me that if I do the business they want to put me on a show in Dublin. They’ve got Jason Quigley and people like Aaron McKenna who could also be on the card.
“And then they have also suggested fighting Lemieux in Boston on St Paddy’s weekend if he beats Saunders.
“These are all just details though. I believe I own that title already, I don’t care who has it. That’s why I write it down each night.
“If it all goes well on Saturday my next fight could be for the world title – how does that happen? I’m a guy who used to train in the woods in Cork on my own.
“I used to pay £100 a week to rent a shed off the nuns and hit the bag. I used to take my first born down there and just put her in the walker while I trained.
“Now look at me now, it’s all aligning, it’s going to happen.”