I will knock out Sonny Bill: Gallen

Cronulla Sharks skipper Paul Gallen has sensationally boasted he would knock out Sonny Bill Williams in any potential mouth-watering fight.

Gallen, appearing on Nine's Sports Sunday, said cross-code hopper Sonny Bill's luck will finally run out at if the two ever crossed in the ring.

"I'll knock Sonny Bill out," Gallen said to roars of approval from his fellow panelists.

"The problem is Sonny's had everything go his way since he was 14.

"Contracts go his way and that's the problem at the moment.

"We're trying to negotiate but (Williams' camp) want it all their way.

"I bring as much to this party as they do."

A showdown between the two sporting superstars has long been anticipated since both footballers donned the gloves.

However rumours have turned into a concrete possibility with Williams announcing a fight would be organised at the end of both player's domestic seasons.

And Gallen said the time was right for action to replace fighting words.

"It's been spoken about for four or five years," Gallen said.

"The first year or two I was a little hesitant to do it.

"But certainly the past two or three years I'd been saying 'let's get it on'."