Seibold is set to switch codes after taking up an offer to assist England rugby coach Eddie Jones ahead of the 2023 World Cup, announcing the move just prior to the start of the NRL finals series.

Brought in this year on a one-year deal, the controversial former Brisbane Broncos coach was initially hired in an advisory capacity as a sounding board for coach Adam O'Brien and as a mentor for the club's other coaches.

But mid-season, his position changed somewhat with O'Brien giving him more of a hands-on role with the side's defence. Over the back-end of the season, the Knights won seven of their final 10 games off the back of more resolute defence to qualify for the finals.

It's understood there were discussions around a potential replacement for Seibold with names such as Paul Green, Paul McGregor, Dean Pay and Cameron Ciraldo all tossed around. Bringing in an attack-orientated assistant was also spoken about but they are thin on the ground.

Former Sharks coach and ex-Knights player John Morris would have been a consideration had he not already been appointed assistant to next year's new South Sydney coach Jason Demetriou.

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In the end, it was decided not to fill Seibold's position with the club confident their existing coaching structure under O'Brien, that includes Willie Peters, Rory Kostjasyn and Eric Smith, and new specialist halves coach Blake Green, is all that is needed.

"Seibs came in at the start largely to coach our coaches, not as an assistant," CEO Phil Gardner told the Newcastle Herald. "It was made very clear to him and to everyone else that it was going to finish at the end of this year.

"He did a good job with us in the time he was here but both Adam and I and Bedsy [head of football Danny Buderus] are comfortable with the coaches we currently have with the addition of Blake Green. We believe they will get us to where we want to go to next year."

O'Brien said the appointment of current Penrith high performance boss Hayden Knowles will also strengthen the coaching department.

"I'll use Hayden a lot more in the coaching area. He is more than just a performance coach," O'Brien said.

"He does actual footy stuff too - particularly around the transition stuff between attack and defence. We'll also have Greeny there as well working throughout the club with our halves."

Despite his side's attack being heavily scrutinised, O'Brien said he has full confidence in his attack coach Peters, who will benefit from having the entire spine together, fit and healthy, for the start of pre-season training in November.