According to Danny Williams it won't be a fist that ends his boxing career. It will be his faith. Since embracing Islam five years ago Williams has gone countless rounds with his conscience. His dilemma is reconciling proficiency in a sport based on violence with a religion that preaches one man should not use his hands to harm another.
Williams, a gentle giant away from the ring but a vicious puncher inside the ropes who knocked Mike Tyson almost senseless in June, acknowledges the day is coming when he'll have to hang up his gloves.
"To me, God is the most important thing and boxing is nothing," he said. "I've got to do what is pleasing to God."
But not yet. Not when a dream can be realised at the Mandalay Bay Arena here on Saturday when he challenges Ukraine's Vitali Klitschko for the world heavyweight championship.
Williams was a mere babe when his father, Augustus, had a dream that his son would one day rule boxing's blue riband division. From that moment a career path was set.
Rudimentary instruction in boxing began when Williams was just four. By the age of eight he was a reluctant attendee at a gym near the family home in Brixton.
Williams recalled: "I didn't like it but my dad is very strict and you have to do what he says."
Now dad's dream has become his dream, too. And this close to the fight that could define his career, Williams has no compunctions about employing traditional rhetoric.
He says he is "ready to rumble" and in a low voice laced with menace the 31-year-old warns he will "bash up" the champion Klitschko.
Promoters love this kind of language. It helps sell ringside seats and subscriptions to Sky Box Office, which is televising the showdown in a double-header with Ricky Hatton's WBU light-welterweight title defence in London earlier on Saturday. But away from the gaudy lights of The Strip, Williams has spoken about the contradictions of being a boxer and a Muslim.
In a BBC World Service documentary Williams reveals how, at the age of 17, he had a feeling "there was a God and he needed to be worshipped".
He said: "Because we were in a Christian country and my mum was a Christian I felt that was the only religion. So I went into Christianity."
Many of Williams's friends from teenage years spent roaming the rough streets of south London are now in prison or dead. If he suffered temptation to stray from an honest path, his new faith helped keep him on the straight and narrow.
"It stopped me going to clubs," said Williams. "And I stopped drinking. In anything I do I like to devote myself 100 per cent to it, so I really devoted myself to being a good Christian and living the life as a Christian."
Like many boxers who don't conform to the popular perception of those who fight, Williams is a deep and complex man. And in quieter moments he began to question the worship of Jesus as God. He explained: "I just believed he was a prophet, one of the greatest prophets, but I didn't believe he was God. I tried to force myself into believing it, to be a good Christian, but it just wasn't in me.
"From then I started to study other religions. I looked into Judaism, I looked into Islam and after many years of studying I became a Muslim.
I felt really relaxed, really comfortable that I was in the religion of God. I really felt at peace."
Ironically, Williams claims a religion which places an emphasis on gentleness helped him resurrect a boxing career that was on the ropes following the loss of his British and Commonwealth titles to Michael Sprott at the start of the year.
Prior to fights, Williams would get so stressed he would often break down in tears. "But when I became a Muslim, I was able to believe everything was in God's hands," he said.
The dramatic consequence of that belief was the savage flurry of punches that effectively ended the career of Tyson, a former undisputed champion of the world.
Williams's reward for that shock fourth-round victory was a shot at the championship. But to take it he has had to pitch up in Las Vegas, a city where alcohol is on tap 24/7, where gambling is the way of life and where lust lurks on nearly every street corner. All, in fact, that is anathema to Islam.
He has tried to strike a balance between belief and ambition. Williams said: "The only problem is me going in the ring and hitting people. You are only in control of what you do. I can't be in control of what other people do."
Indeed, there are principles he simply won't compromise.
Williams revealed: "For the Tyson fight I was offered big money, I think it was $50,000, to put a gambling website on my back. I refused it because of my faith. That is something I definitely can't get involved in."
Yet, he is willing to lay his hand, hard, on the cheek of another man.
Williams said: "Yes, there is a conflict. Many Muslim brothers have told me that I shouldn't be in this sport. But they say the Koran was given to Muhammad in pieces and it is the same with us: when you become Muslim you clean yourself bit by bit.
"Me giving up boxing will be another bit I've got to give up. Eventually, I've got to do it."
Heart and Soul: Celebrity I Believe' to be broadcast by the BBC's World Service on Wednesday
FIVE FIGHTING MUSLIMS
MUHAMMAD ALI Changed his name from Cassius Clay in 1964 after becoming world heavyweight champion.
AMIR KHAN Students at Bolton's Noorul Islam Mosque prayed for Khan during the Athens Olympics.
MIKE TYSON Claimed he converted to Islam while serving a prison sentence for rape.
CHRIS EUBANK Embraced Islam in 1997, taking the name Hamdan. Arrested last year outside Downing Street for protesting against the Iraq war.
NASEEM HAMED The former world featherweight champion
once narrated a special programme for the BBC called
"Prince Naseem's Guide to Islam".
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