Former Bulldogs NRL star Sonny Bill Williams has apologised to the teammates and fans he abandoned when he walked out on the club and the code last year.

Williams, back in Australia ahead of his first professional boxing bout in Brisbane on Wenesday night, told the Nine Network's The Footy Show he regretted the way he fled Australia to take up a rugby union deal with Toulon in France.

"It's definitely not the way I should have come out and done things," Williams said.

"I was a little bit upset with myself that I didn't apologise to the boys.

"If I had my time over again I would have rung every single player in the team.

"I know a lot of the boys were let down by my actions.

"At the time I thought if I did ring some of them, knowing how they were like, knowing how passionate they were about the club, they wouldn't understand, so I just thought it's better left unsaid.

"I would definitely change that."

The Bulldogs initially attempted to block Williams' move after he skipped the country but eventually settled on compensation.

After struggling initially with injuries and the machinations of the 15-man game, Williams found his feet in the centres at the French club and was rewarded with a call-up to the Barbarians side to play the Wallabies on June 6.

Having apologised to his teammates, who went on to finish last in 2008 as they struggled to put the upheaval of Williams' departure behind them, the former Kiwi international then turned his attention to Bulldogs fans.

"I didn't apologise to the fans (when I walked out) and I guess that's what I want to do," Williams said.

"Especially to the Bulldogs fans, the young kids that really looked up to me, I just want to say I'm sorry for all the heartache and the problems I've caused.

"But there's always light at the end of the tunnel, look how good the Dogs are going this year. I'm happy to see that. I've got no animosity towards the club."

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