Hetherington, 26, has been chased by a host of clubs, including Canberra, Wests Tigers, St George Illawarra and the Dolphins, but it is understood family reasons have played a big part in his decision.

His father, former Canberra Raiders premiership winner Brett Hetherington, lives in Belmont and Jack's partner is also a Novocastrian.

Hetherington, currently recovering from a shoulder reconstruction, has played in 43 NRL games for the Bulldogs, Panthers and Warriors. He would have played significantly more, except for a dubious judiciary record that has resulted in multiple suspensions.

The Knights were willing to take a gamble after their high-performance manager, Hayden Knowles, provided a strong reference as to his character and athletic ability.

The former Valentine-Eleebana junior was last year rated the fastest forward in the NRL, according to GPS-tracking data.

He is capable of playing front row or back row, and the Knights see him as an ideal replacement for Warriors-bound Mitch Barnett.

Meanwhile, the Knights have confirmed Canberra back-rower Adam Elliott is joining them on a three-year deal, while promising utility Simi Sasagi has re-signed for a further two seasons, until the end of their 2024 campaign.

Sasagi, an Auckland-born 21-year-old, made his NRL debut in round 11 last season and now has eight top-grade appearances to his name, including five this season.

AAP reports: Penrith co-captain Isaah Yeo has been ruled out of Sunday's game after his head knock in State of Origin I.

Yeo, who has a history of concussion, was cleared by the on-field doctor and wasn't taken off for assessment despite clearly stumbling back into the NSW line after the first hit-up of the game.

Blues assistant coach and Penrith board member Greg Alexander told SEN radio on Friday: "He won't play."

No call has yet been made on halfback Nathan Cleary, who copped a pasting from Queensland in Wednesday night's defeat, but the likes of Stephen Crichton, Brian To'o, Liam Martin and Jarome Luai are likely to figure.

Newcastle are likely to pick Queensland duo Kalyn Ponga and Dane Gagai, both of whom starred in in Origin 1.

Gagai and Ponga have been resting and recovering since their heroics on Wednesday night but are expected to confirm their availability at Newcastle's captain's run on Saturday.