Conor McGregor has boxing skills, but enough to beat undefeated Floyd Mayweather?

Before Conor McGregor had even heard of mixed martial arts, he wanted to be a boxer. He first stepped into Crumlin Boxing Club nearly 20 years ago in muddy football boots and started punching a heavy bag.

McGregor returned constantly for the next seven years, determined to become tough enough to dissuade bullies in his Dublin neighbourhood. He competed in amateur boxing matches against opponents of all sizes and shapes over the years, developing tenacity and power.

"There were no weight rules, no limitations on who you could fight," McGregor recalled Wednesday. "We would just have an opponent assigned to us. That was always the joke: Everybody at the Crumlin Boxing Club had to fight heavyweights, no matter what size you are. But it was a good lesson. You must be prepared for any eventuality. You must be ready to fight. That's how I was brought into this game."

McGregor is on top of the fight game this week before his Saturday showdown with Floyd Mayweather (49-0), the most accomplished boxer of his generation. McGregor, a former plumber who has never had a professional boxing match, will make roughly $100 million for stepping into the ring for the first time in the spectacle of the summer.

And though McGregor moved into MMA training in his teens and eventually rose to win two UFC belts, he is no boxing neophyte. While he has other strengths, McGregor's MMA career has been built in large part on his boxing-bred punching power, which is considered exceptional by his sport's standards.

Oh, and he also doesn't lack confidence, which is no small thing when facing odds as daunting as McGregor's chances against Mayweather.

"No fighter can train for what I bring into the ring or into the octagon," McGregor said. "I am too skilled. I am too diverse. My movement is too much for them. All of these men will fall."

But for McGregor to make Mayweather fall, he'll either need to land an astonishing home-run punch, or he'll have to show more creativity and sustained boxing skill than MMA usually demands.

While McGregor's versatility and smarts have made him the UFC's biggest star, he can use only one discipline against Mayweather — and no serious people outside McGregor's camp doubt Mayweather has more boxing skill. Still, McGregor has devoted himself to boxing in recent weeks, bringing in former champ Paulie Malignaggi among his many sparring partners and recruiting Joe Cortez, the veteran boxing referee, to instruct him on the finer points of etiquette.

"Fighting in Vegas, I just don't see how Conor out points him (for a decision)," UFC President Dana White said. "Conor is going to get in there to rough him up and try to knock him out."

White and McGregor's other fervent backers believe in his one-punch knockout power, which he showed most memorably in dethroning longtime UFC champion Jose Aldo. But one-punch knockouts are rare in 8-ounce boxing gloves, which diffuse the impact of a blow more than tiny UFC gloves.

McGregor's ability to pull off perhaps the most improbable upset in sports history likely rests on his chances to land not just one punch, but repeated combinations of blows on Mayweather, who has shown a decent chin on the few occasions he has been hit in the past decade.

If McGregor can't consistently hit Mayweather — and nobody has consistently connected against Money May in over a decade — he can at least avoid embarrassment by not getting knocked out — and there is no doubt McGregor can take a punch. His sparring partners have spoken of his tough chin, and it was evident last year in his two UFC brawls with Nate Diaz. Their second bout in August 2016 devolved into a brutal stand-up fight that left both men bloodied and bruised.

McGregor's disregard for defence in that bout — or his inability to defend himself from repeated head blows — could be decisive when facing Mayweather, who might be the most precise puncher in the sport. McGregor claims he has worked on defence during his training camp, but his predictions for the fight invariably return to his belief in his own power.

No matter what happens to McGregor at T-Mobile Arena, he will rely on the skills he first learned at the Crumlin Boxing Club, where his mother Mags still works out. The club will be full of his fans when it screens the fight at about 5 a.m. Sunday morning.

"You will see the culmination of everything I've learned and studied," McGregor said. "A great many people helped to get me to what you will see this weekend."