NRL star turned boxer Paul Gallen has given fellow league convert Sonny Bill Williams a great reason to keep boxing, with the former Sharks and New South Wales star claiming to have made $25million from the sport.

Gallen will square off against State of Origin rival Justin Hodges on Wednesday night in Sydney in what is likely to be his last professional bout.

Meanwhile, Williams' boxing career is at a crossroads after he was dismantled by former UFC star Mark Hunt earlier this month.

There has long been hope that Gallen and Williams would meet in the ring but the former Cronulla skipper said there is no way that will happen now.

But while Gallen's career is winding down, he said Williams should cash in while he can.

'There's definitely plenty of money to be made,' Gallen said.

'I just don't know if Sonny wants to do it. But if I were Sonny I wouldn't be stopping.

'The guy is 37. And look at what has happened with me from roughly the same age.

'I've grossed $25 million over the past three years. That's a lot of money.

'So $25 million in three years … no, I wouldn't be leaving if I were Sonny.'

The staggering earnings of Gallen in recent years make his rugby league pay packets look minuscule by comparison.

If you assume that Gallen is paid $650,000 annually to play for an NRL club including third party agreements, plus gets $30,000 for three State of Origin matches and $25,000 for an average of four Tests with the Kangaroos each year, his annual income would be $840,000 before tax.

But while the lure of the almighty dollar is there, Gallen said there is zero chance now of fighting Williams.

'I'll never fight Sonny Bill, I'll say that right now, even if they guaranteed $5 million in my bank account before the fight, because he'd make $5 million too,' Gallen told News Corp.

'He had his chance. We should have fought twice over the last couple of years. The ego and arrogance from their side is at a level that I don't want to be involved in.

'No Limit don't want to be involved with them, No Limit's the biggest and best promoter in Australia and they don't want to be involved with them? What does that say?

'That fight will never happen, I'm not going to talk crap about Sonny. I was asked if Sonny should fight again, yes, Sonny is 37, he's got plenty left in him.

'Look what I've done in the last three years, grossed $25 million. He could do the same, make millions. But I will not fight Sonny Bill, ever.'

Meanwhile Williams' fans can take heart in the fact the Kiwi has returned to the ring for training after his loss to Hunt.

'Alhamdullilah for all the blessings in my life. Without experiencing the lows, you don’t fully appreciate the highs. Seki [so good] to be back in the square office,' he posted on Instagram this week.

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