Newcastle boss Phil Gardner declared on Wednesday that the Knights would embark on a search for character, with a new coach wanted by November.

Gardner also confirmed senior Newcastle players would be consulted in the process, after Brown confirmed he would quit at season's end.

It came on a dramatic day in the Knights' search.

Roosters assistant Craig Fitzgibbon pulled himself out of the race on Wednesday, following in the footsteps of Queensland mentor Kevin Walters.

Fitzgibbon had been considered a likely candidate, having formed a close bond with the former Roosters at the Knights.

It leaves O'Brien, a former Batemans Bay Tiger, as the most likely option, having cut his teeth under Craig Bellamy at Melbourne before moving to the Roosters this year.

Knights players wouldn't back any possible replacement so soon after Brown's resignation, but forward Tim Glasby knows O'Brien best from his time at Melbourne.

"I've obviously had a lot to do with Adam over the years and I highly rate him," Knights and former Storm forward Tim Glasby told AAP.

"He is a terrific person and a really good coach. As for whether he is right for here that is for the hierarchy to decide.

"But I'm sure whatever Adam does he will do well at because he is a great bloke with a terrific work ethic and great knowledge of the game."

Melbourne assistant Jason Ryles could be another option if the Knights go for an untested product, having been at the Storm for four years.

Brown's Newcastle assistant and Tonga mentor Kristian Woolf has also been mentioned, but has also been linked to the top job with St Helens in the English Super League.

Garth Brennan has also previously been an assistant at Newcastle, while Anthony Griffin, David Furner, Trent Barrett and Geoff Toovey are the more experienced options.

Former North Queensland and Gold Coast mentor Neil Henry has not been contacted, despite being one of the most recent coaches out of work.

Shane Flanagan's name has also been mentioned, but it would appear the NRL won't clear him to return after he was deregistered earlier this year.

"Now the coach has allowed us to scour the market, we will," Gardner said.

"We intend to start with character. We have had a coach with fantastic character. Anyone who doesn't pass the character test will not be coming to Newcastle.

"We've got to get a person who at least has the integrity levels of Nathan. There aren't a lot."

Gardner also said Brown's unique open-ended performance-based contract would not necessarily be replicated with his replacement.

If O'Brien is hired as the new Knights coach, he will become the third Group Seven talent to be in charge of a NRL team in 2020, with Batemans Bay's Brad Arthur in charge of the Eels and Milton-Ulladulla' Justin Holbrook recently appointed for the Titans gig.