It's understood Watson told coach Adam O'Brien and his Newcastle teammates of his decision on Tuesday morning.

Watson rejected an offer of a three-year extension at the Knights worth around $350,000-a-season to return to the Roosters, the club who gave him his start in the NRL, on a deal understood to be for less money.

The utility star, who played his 100^th NRL game against the Sharks on Sunday, has played 62 of those with the Knights over the past four seasons.

As late as last week, O'Brien was still confident of retaining the 25-year-old despite the Roosters' interest.

He claimed the club had made him a good offer.

"From what I understand, it's more than competitive with our rivals, so I think now it comes down to a decision from Connor himself on where he sees himself next year," O'Brien said prior to the Sharks game.

"But certainly from the club's point of view, I think it's more than competitive, our offer, and we do value him, we all love Connor.

"I'd love for him to continue with us and be a member of, hopefully, any future success we have."

# Meanwhile, Knights backrower Tyson Frizell has accepted a one-match ban for a grade one careless high tackle and will miss Saturday's clash against the Bulldogs on the Gold Coast.