The former All Black sat out Sunday's pre-season match at Castleford, despite being named in McDermott's 21-man squad, and instead was among the 3,346 spectators at the Mend-a-Hose Jungle to witness a 16-10 victory for his new club.

"Sonny Bill will be available for round one," McDermott said. "Whether we play him or not, we're just deciding on his fitness.

"That journey from rugby union is not to be sniffed at and we're taking an approach he's got to be good for the final third of the season.

"I know there's an anticipation around him but we're not going to rush him and run the risk of him pulling something.

"He's been playing a specific role in a different sport for a number of years and that transition will take some time."

The 34-year-old Williams, whose last match was in the Rugby World Cup in November, will attend the club's pre-season media day at the Etihad Campus on Wednesday and the official Super League launch at Headingley on Friday.

But, even if he plays in the Canadian club's opening league game, against Castleford at Headingley on February 2, he is set to miss a couple of early-season matches as he plans to fly back to New Zealand for the birth of his fourth child.

"He highlighted this when we recruited him," McDermott said. "I think it's due around round three."

Australian Associated Press