Williams makes good fist of the fight game

Sonny Bill rings changes with boxing career but still wants to be new Lomu

If you have ever wondered what would happen when the mega-hype of boxing ran into rugby's "no 'i' in team" and fair play to all men, meet Sonny Bill Williams. The Crusaders and All Blacks centre and part-time pugilist is in London for the Super Rugby fixture against the Sharks at Twickenham today and he has brought his motormouth with him.

"Man, David Haye is the man," he enthuses in a pre-match conflab. "I reckon he could chuck on some boots and go out in the 15-man code. Jonny Wilkinson? He's like an animal in the gym. No disrespect to the No 10 England have there now [Toby Flood]... but if they were to go all the way in the World Cup, Jonny would have to be at the forefront."

Williams played with Wilkinson last season at Toulon in France; before that, the Auckland-born, Samoan-descended giant of New Zealand rugby league was vilified in Australia for his overnight defection in 2008 from the NRL to French rugby union. Along the way he has taken to boxing and he has an extraordinary agreement with the New Zealand Rugby Union that he can fight twice this year – a World Cup year – in proper, promoted fights that earn the heavyweight Williams a hefty £100,000 a time.

He had two gentle workouts last year before a notably more serious points verdict against Australia's Scott Lewis over three rounds in January. There is talk of another fight in June which may raise funds for victims of the earthquake in the Crusaders' home city of Christchurch – though in classic fight fashion Williams turns suddenly coy over the salient details.

"When I find out exactly what's going on, I'll talk about it," he says. "In the last fight, I was pretty proud of myself. It showed I could box, I thought." Was he surprised at the NZRU allowing Dan Carter's right-hand man to stick his chin on the line? "Yeah, I was actually," he says. "But boxing has just lit a fire in me that I can't put out. It just gives me that extra edge. It was always in my blood. My mother's father was a boxer and obviously my dad is of Samoan heritage and he's never shied away from a knuckle dust-up."

If the All Blacks win the World Cup, might he switch his full-time profession, while still in his mid-20s? "I feel that the heavyweights these days are pretty one-dimensional," he says. "If any bloke over 100 kilos puts one on your chin you're going night-night, but I'd back myself to go quite some distance."

For now it is rugby that shines the brightest light on Sonny Bill and after his All Blacks debut against England last November, he returns to Twickenham sandwiched in an exciting midfield between Carter and the uncapped hope Robbie Fruean. The latter is a centimetre shorter and four kilos lighter than Williams's 191cm and 108kg. And you thought England's centres were big.

"Robbie has a bit to learn but as time goes on he gets better and better," says Richie McCaw, the Crusaders' captain who is injured for this experimental trip to play South Africa's Sharks. "He had open-heart surgery a couple of years back, so to see him and Sonny Bill together, they are making quite an impression. With ball in hand they're a real threat."

It's no hype to say Williams feels comfortable with the world's best (at Toulon he also played alongside former All Black captain Tana Umaga). Asked if he would like to make a Jonah Lomu-esque impact on the World Cup he says: "I am not going to lie, I would love that to happen. I believe if I play a good 20 games before the World Cup I will have that confidence to make the squad, make the team and add what I can add.

"The higher you go up, the tougher the pressure is, mentally. Jonny Wilkinson was somebody who gave me confidence, saying that he had played with a lot of great players and he rates me up there. He is not the biggest bloke but every tackle he does, he flies in like a madman. If you see him in the gym, the way he trains, the man is like an animal. He has still got a lot of gas in the tank."

Divvying up the "take" is fundamental in the fight game and so it is today, with a fiver a ticket (plenty are available on the gate) going to the Red Cross Christchurch fund. Each of the principals has his own experience of the quake: Carter taking a shower after training, McCaw shopping, Williams in a spa at the gym thinking the ceiling was about to fall in.

"We're footy players and entertainers," says Williams, with a smile and a flex of the biceps and a shadow-box flurry of fists. "If we can perform and show a little razzle dazzle to the people who really love the Crusaders or All Blacks then it's great."

Crusaders v Sharks is on Sky Sports 2 today, kick-off 4pm