“It’s big, it’s humbling and it’s amazing,” Carl Frampton says of his arrival in Las Vegas on the back of multiple awards confirming him as the fighter of the year in 2016. Frampton is preparing to defend his WBA featherweight world title on Saturday night against the man he defeated in a thrilling fight in New York last summer. The Vegas rematch is likely to replicate his first savage battle with Léo Santa Cruz. Frampton produced such a compelling performance, studded with precision and grit, that American writers and fans were stunned.

The 29-year-old from Belfast won the most prestigious poll in boxing when he was named Ring magazine’s Fighter of the Year award for 2016 – to match the accolade given to him by ESPN and Britain’s venerable Boxing News. Frampton had begun 2016 with a comfortable points victory over his British rival Scott Quigg, in a super‑bantamweight world title unification contest that drew weeks of heavy hype and 20,000 people to Manchester. He now looks far stronger in the higher weight category.

“This T-shirt is a little tight so it looks like the muscles are bulging more than they really do,” Frampton says with a wry smile. “But I am much stronger at this weight. I felt the benefit against Santa Cruz. It was my first fight at featherweight and it was special to hear what all the American reporters were saying afterwards – and for them to vote for me as their fighter of the year is pretty incredible when you think where I’ve come from.”

Frampton grins and shakes his head at the sweet wonder: “From Tiger’s Bay in Belfast to the MGM in Vegas … it’s been some ride so far. And the best is still to come.”

Before we go back to the beginning, when he was a little Protestant boy growing up on the interface between loyalist and republican communities, Frampton looks ahead to Saturday night’s certain ferocity with relish. For such a friendly man outside the ring, Frampton harbours a great fighter’s delight in the fact that he works in such a dangerous business. He also nurtures a cool certainty that he will prevail once more against a former three‑times world champion and determined Mexican warrior. Santa Cruz was hurt by Frampton in the ring but he was wounded much more grievously by the loss of his title. He will come after the new champion with renewed force.

“I know he will,” Frampton says. “It’s going to be hard but I also know I can do certain things to make it easier for me. I think that’s the difference between us. I can adjust. But I don’t see any way Léo can change his game. He will just come after me as hard as last time. He threw 1,100 punches at me that night. He can’t do much more this time … but, even if he does, it will just give me more chances to nail him.”

Frampton sips his green tea when asked to detail the ways in which he can improve. “I’ve watched the first fight a few times and I made plenty of mistakes. Sometimes I stood my ground too long. Even when I moved back I was doing so in straight lines. I got clipped with combinations as he has pretty long arms. So if I take one step and then meet him and counter I can cut out so many mistakes.”

Santa Cruz threw 1,100 punches at me that night. He can’t do much more this time.

Shane McGuigan, his canny young trainer, told me Frampton could have out-boxed Santa Cruz comprehensively – had he not become caught up in the raw fervour of the night. “Yeah,” Frampton nods, “Shane thought I was staying in the pocket too long and sometimes just throwing for the sake of it. You feel you need to match Léo’s volume of punches. But sometimes it’s better to wait and pick your shots and hit him much more cleanly with very controlled shots rather than just going “waaaaaagggghhhh!” with five or six punches.”

Frampton mocks his hell-for-leather torrent of blows – knowing he is at his best when operating as a highly intelligent counter‑puncher who picks apart a ceaselessly aggressive fighter like Santa Cruz. “But I still did really well last time. You’d have to say it was the best performance of my career. I wanted to stamp my authority from the start and I really hurt him in the second round and quite a few times after that. He tried to hide it but his legs wobbled. I hit much harder than he does. It’s just about being smarter this time – hitting him clean and putting more emphasis into those shots. If I do that, I think I can fucking knock him out. I really do.”

Bravado is not Frampton’s language. He prefers to talk in grounded good sense, respecting his opponents and mocking himself if he feels people are talking him up too much, and so this statement rings with fresh force. It promises to be another desperately hard fight but Frampton clearly believes in his own concussive power – allied to his superior boxing ability. He also turns 30 next month and, after 23 years of fighting, experience pours out of him.

Carl Frampton reacts after beating Leo Santa Cruz in New York in July 2016. Photograph: Andrew Couldridge/Reuters

The story of how Frampton, like his manager Barry McGuigan before him, found a way out of sectarian violence and united Protestants and Catholics in support of him has been told before. But his first fight as “a scared wee boy” belongs to lesser-known territory.

“I was always quiet and even timid,” Frampton admits now. It was different once he pulled on the big gloves and ducked through the ropes. Little Carl loved sparring. The painfully shy kid who was frightened of the loud, swaggering boys on the streets in Tiger’s Bay became ferocious between the ropes. Carl was seemingly fearless and he was good. It was not long before his first trainer Billy McKee drove him to a hotel just outside Portstewart, an hour’s drive from Belfast. There was an opening at a club show for a seven‑year‑old to face a boy from the Scorpion club in Ballymoney, in County Antrim.

“A few years ago I read about [the boy he fought],” Frampton remembers. “At least I think it was him. A newspaper report said he’d ended up in jail after stabbing another man. When I was seven he seemed so much tougher, rough and bigger than me. I was just a very wee boy shitting himself.”

Thick clouds of blueish smoke hung in the air as, at the hotel, rowdy men puffed away and made a racket while watching the fights. They whooped and hollered as the two boys, Frampton in the blue corner and the other in the red, faced each other. The crowd was in the mood for a scrap.

His tiny heart thundered in his bony chest and Carl felt so petrified he could not absorb a single word of the last few instructions McKee gave to him in the corner. “It was a bit terrifying,” Frampton says now, “facing this kid from the Scorpion club. But then the bell rang and instinct took over. It was quite a hard fight. But I definitely got the better of him. The kid was backing away and I was tearing after him. I won that fight easily – even if they didn’t name a winner because it was just meant to be exhibition contests until you were 11. But it was a proper fight all right. And I loved it. Billy was proud of me and I couldn’t stop smiling.

When I was seven he seemed so much tougher, rough and bigger than me. I was just a very wee boy.

“I was only confused when, afterwards, they offered us sandwiches. I was fucking starving but they were these ridiculous little things, cut into tiny rectangles, with the crusts taken off. I said: ‘What the fuck are these? I want a proper sandwich.’ I still ate them and we went home very happy.”

Carl loved boxing and he didn’t mind being hit in the face. Most of the time, he slid away from a swinging punch and made the kid facing him gasp after a crisp combination of his own. Carl only cried when he lost – which was very seldom as a decorated amateur.

Frampton boasted a perfect 22-0 record, after seven years as a pro, when he faced the more favoured Santa Cruz last July. He allowed me to be with him in his locker room in the last hour before the opening bell. Unlike his teeth-chattering fear as a little boy in Portstewart his mood in Brooklyn was quiet but contained.

Shane McGuigan wrapped Frampton’s hands. They chatted a little to Santa Cruz’s brother, José, who had arrived to ensure the wrapping was done correctly. José remembered how injury had ended his ring dreams. Frampton nodded sympathetically.

Once the wrapping was done David Haye, the former world heavyweight champion now also trained by McGuigan, strode into the dressing room. “All right, big man?” Frampton said with a grin.

Craig Frampton, Carl’s dad, dropped by briefly. His face was etched in tension as he wished his son well.

McGuigan smeared Vaseline around Frampton’s eyes and cheeks. He spoke to his fighter, reminding him what to do when all hell broke loose.

Marvin Gaye, singing like a sweet and profound ghost from the past, echoed above the muted voices. What’s Going On rang out as Frampton’s boots tapped in time to the old soul classic.

Frampton’s gold gloves shimmered beneath the bright lights. Marvin Gaye faded away and Wilson Pickett sang, just before 11pm, that he was “gonna wait till the midnight hour, that’s when my love comes tumbling down …”

The challenger stood up. He flexed his neck and rolled his muscled shoulders. Frampton banged his gloves together. Jackie Wilson had taken over the sound system. “Your love,” he crooned, “keeps lifting me, higher and higher …”

Frampton made eerie cries as his blurring gloves smacked hard into McGuigan’s pads. Years of hard work were about to reach a crescendo. Anything could happen: a beautiful victory or a crushing defeat, controversy or drama, even death or glory.

There was a knock on the closed door. It swung open and a New York official said three simple words. “It’s time, gentlemen …”

Afterwards, and revelling in victory, all the risk and danger felt worth it. Carl Frampton was the King of New York. He was the new King of the Ring. But he was still steeped in humility and gratitude. The next afternoon, in Annie Moore’s, a heaving bar in Manhattan, Frampton allowed his devoted army of 1,200 travelling fans to knock back as many pints as they liked on him. He paid for every drink as the Guinness and champagne flowed with the songs and the selfies of a world champion who made them all feel so happy and united.

“Yeah, we turned New York into Belfast for a weekend,” Frampton says now with a smile. “Most of them, and a hell of a lot more, are coming to Vegas. I don’t want to let them down. There is so much riding on this one. My name and my face are all over Vegas. I’m the world champion and some people’s fighter of the year. So I am determined to show everyone that last year was the start of something special. I hope to be even better this time.”