Williams has signed with Counties-Manukau for the provincial competition, but the New Zealand Rugby Union has confirmed he won't have to take the field to make the All Blacks squad.
If the Roosters make the NRL grand final, it's highly unlikely he will play for Counties as their last round robin game is four days after the league season.
NZRU CEO Steve Tew said today if the coaching staff wanted him in the squad, he could play.
According to Tew, the board have given the All Blacks coaches the discretion to bend the rules and take Sonny Bill.
After announcing the signing of Williams in June, Steelers coach Tana Umaga said he was rapt to be reunited with Williams, after coaching the league convert at French club Toulon for two seasons from 2008-2010.
"Sonny is an outstanding man, whose work ethic, ability and motivation are exceptional. He will be a great role model to our younger players and an inspiration to the young people of South Auckland."
Meanwhile, Tew also said Japan and Singapore's proposal for their Super Rugby inclusion has been received, but the early submission is slightly unsatisfactory.
