Sonny Bill Williams rates his next heavyweight boxing bout as more of a challenge after winning a controversial decision over Francis Botha almost two years ago.
The 29-year-old cross-code star believes Chauncy Welliver is more durable than the South African but is backing his superior fitness to come out on top against the giant 137kg American at the inaugural Footy Show Fight Night in Sydney on January 31.
Williams says he will wear the 70-fight veteran down over eight rounds due to his greater athletic ability but is mindful of his opponent's experience.
"He's a classy fighter. You can't train experience, you've got to be in the ring doing it," he told reporters in the New Zealand city of Hamilton on Wednesday.
"It's definitely a challenging fight but with the occasion I knew I had to take on a fighter of this calibre.
"It's a little bit daunting but hopefully I get over the top of him and have a big year this year."
Williams, who's switched back to rugby after two seasons with the Roosters in the NRL, has impressed Chiefs coach Dave Rennie by setting a personal best in pre-season fitness training.
"He's phenomenal. He's in good nick and it's a really good signal him coming in and being in such good condition this early in the season," Rennie said.
He has no concerns about the safety of his marquee player entering the ring with a big hitter.
"From our point of view it's been really positive him boxing, as it puts him in the sort of condition he is in now. It's highly motivating for him and you need that variation," the coach said.
"We have a few issues around concussions already.
"It's just part of the game. It's part of the risk you take boxing and it's no different playing footy and training."
Williams, whose previous bout was cut short by two rounds with him seemingly heading to defeat against Botha, remains philosophical about the fight when asked if he had a point to prove to himself and others.
"It may seem like that from the outside looking in but I'm just motivated by the challenge."