Watch: Sonny Bill Williams clashes heads with ex-AFL star ahead of boxing return

Former All Blacks star Sonny Bill Williams has gone head-to-head, literally, with ex-AFL bad boy Barry Hall ahead of their fight in Sydney on Wednesday.

Williams, who played 58 tests and won two World Cups with the All Blacks between 2010 and 2019, will make his return to professional boxing against Hall in what's expected to be a fiery cross-code clash.

Hall, a 2005 AFL champion with the Sydney Swans who was renowned for his controversial acts of on-field aggression throughout his 15-year footballing career, lived up to his reputation at his pre-fight weigh-in with Williams on Tuesday.

Weighing in at 97.8kg on the eve of the bout Hall refused to back down against Williams, who stood more than 11kgs heavier than his opponent at 109.1kg.

That didn't dismay Hall, though, as he drove his head into the face of Williams when the pair came together for a face-off shortly after they tipped the scales.

Williams was refrained by security guards while continuing to stare Hall down. The duo then traded some words with each other, before Williams pushed Hall away after having shaken hands with his opponent.

At the age of 45, Hall is nine years older than Williams. That, in addition to the sizeable difference in weight between the two boxers, has seen the bookmakers place Williams as the slight favourite for the fight.

After having also won two NRL titles with the Canterbury-Bankstown Bulldogs and Sydney Roosters, Williams retired from both league and union last March.

Since then, the undefeated former New Zealand heavyweight champion has returned to the boxing ring, ending a six-year hiatus when he defeated Australian fighter Waikato Falefehi by unanimous decision in Townsville last June.

In preparation for this fight, Williams spent time training with WBC heavyweight champion Tyson Fury, former WBO heavyweight champion Joseph Parker and Tokyo Olympics heavyweight bronze medallist David Nyika in the United Kingdom.

Fury's trainer Andy Lee has since gone on record that he believes Williams has the ability to go on and become heavyweight champion of the world.

“I’m not blowing smoke; my ambition with Sonny is to one day fight for the heavyweight championship,” Lee told the Sydney Morning Herald.

“It is well within his reach. With the progression he has made in the last six-to-eight weeks, the way I see him going in the future, with the right fights and the right training he certainly has the ability."

Hall, meanwhile, has fought just once in his professional boxing career - sevens fights fewer than Williams - slugging out an entertaining draw with rugby league great Paul Gallen in 2019.