Sonny Bill Williams has apologised for his emotional tweet last night accusing the judges of being "corrupt" after his good friend Anthony Mundine lost a unanimous points decision to world champion Daniel Geale in their IBF middleweight title fight in Sydney.

Williams tweeted a pic of him with Mundine after the fight, with the words: "Hanging out with @Anthony_Mundine celebrating a victory. We don't pay attention to corrupt judges!!".

But Williams today tweeted an apology, saying emotions were running high last night.

"Sorry about the tweet last night. Emotions were running high just very disappointed for my brother and that's how I saw the fight," the former All Black posted on Twitter.

"No disrespect meant to Geale he's a great champion-fighter and it was a great night."

The Mundine camp was reported to be upset with the decision, which had two judges score the bout 117-111 and the other 116-112, a convincing margin of victory.

But Australian media outlets scanned this morning all agreed with the judges, saying the 31-year-old Geale was a deserving winner. None suggested there was any controversy over the result.

As per usual for a big boxing bout, there was a stellar cast of sporting stars, administrators and politicians in attendance.

NSW Premier Barry O'Farrell, footballer-boxers Williams and Quade Cooper, rugby league stars Todd Carney and Nathan Hindmarsh and FFA boss David Gallop were among the many notable figures.

Australian media have now raised questions over the 37-year-old Mundine's boxing future following the loss, acknowledging that while he was competitive, he lacked the explosive advantage in speed that enabled him to beat opponents in his prime.

As for Williams, he takes on South African Francois Botha in his sixth professional fight in Brisbane next Friday night, suggesting at the weekend that a loss would see him throw in the towel and concentrate on his rugby league career.

He returns to the code this year for the Sydney Roosters in the NRL.

"If I get knocked out then that will probably be the end," Williams said.

"Right now I can see myself doing boxing fulltime in the future, but for that to come to fruition I need to fight guys like this and beat them, otherwise it's a waste of time. "If this doesn't go too well I could just stay in one sport.

"If I lose this fight I will definitely be upset because I know it will probably be the end of it. 
"And if I win, then it opens doors."

- © Fairfax NZ News