Sonny Bill in weigh-in brawl

Sydney - Rugby World Cup winner Sonny Bill Williams has yet to prove he can cut it with the best of the boxing world but the All Black looked every inch the brawler when he came to blows with upcoming opponent Clarence Tillman at the weigh-in on Tuesday.

VIDEO: Sonny Bill Williams in weigh-in brawl

American Tillman took exception to the New Zealand powerhouse centre's trash-talking as they faced off at Hamilton's Ringside Gym and gave him a shove.

Williams responded by punching him on the chin and took a right hook to the face in return.

Australian professional boxer and former rugby league player Anthony Mundine, a friend and stable mate of Williams under manager Khoder Nasser, pulled Tillman to the ground and pushed him into a nearby boxing ring.

Video footage posted on the Internet showed Williams murmuring: "Don't call me homie" as the pair eyed each other before they started swinging.

"If he wanted to I could fight right now," said Williams. "It's on."

Fairfax media quoted Mundine as saying he thought Tillman was out of line.

"I think he's flustered," he added. "That was a very disrespectful thing to do. To dog shot someone like that, he's lost all respect and honour as a warrior and I sure do hope that Sonny makes him pay for that tomorrow(Wednesday)."

Tillman weighed in at over 128kg, more than 20kg heavier than Williams, who has been permitted a limited number of fights by the New Zealand Rugby Union in his one-year contract.

Williams has defeated a string of weak opponents and largely failed to impress in his four fights.

Australia's amateur boxing team captain Luke Jackson branded him "a joke" in local media last week and dismissed him as a "good looking bloke ... but not much of a boxer."

Williams won by unanimous decision but was taken the distance in six rounds against his last opponent, 43-year-old Tongan Alipate Liava'a, who New Zealand media derided as a "sickness beneficiary".

The 26-year-old Williams will take on 34-year-old Tillman, who has a record of 11 wins, eight losses and two draws, for the vacant New Zealand Professional Boxing Association belt at Hamilton's Claudelands Event Centre on Wednesday.

Tillman replaced Richard Tutaki, who was scratched from the fight after being arrested on a number of charges.