On Monday, Knights coach Nathan Brown shocked the NRL when he told his club he would quit at the end of the season, even though his side is still within touching distance of the NRL's top eight.

The catalyst was Brown's belief that Knights list manager Troy Pezet had secretly met in Sydney last week with O'Brien and his manager, Isaac Moses.

O'Brien and Moses vehemently denied that any meeting took place, while Pezet did not return the Herald's calls, but even speculation about it has caused a major upheaval at the Knights and now the Roosters.

O'Brien is firming by the minute for the Knights job after fellow Roosters assistant Craig Fitzgibbon ruled himself out and the NRL said de-registered Sharks coach Shane Flanagan cannot be considered.

Another surprise candidate is Knights assistant Kristian Woolf, although he is tipped to get the vacant job at St Helens in the UK Super League.

Roosters powerbrokers are angry that O'Brien is considering the job just three weeks out from the finals - and just nine months into a three-year deal.

It is understood he has a clause in his contract that allows him to walk away at any stage if a head coaching job becomes available.

The Roosters had originally baulked at the clause, wanting stability in their coaching ranks, before O'Brien gave them a verbal assurance he would not consider leaving until the end of his second season.

O'Brien disputes that he made such a promise.

While O'Brien is adamant he has not met with the Knights, the Roosters are keen to bring the situation to a head so it does not cause any distraction leading into September.

Any decision about O'Brien will be left to Roosters coach Trent Robinson, who declined to comment when approached by the Herald.

Complicating the matter further is the fact that Roosters chairman Nick Politis has had a major fallout with Moses, who is also in the middle of a messy split with star fullback James Tedesco.

While he's been touted as the next big thing in coaching, having dismissed several approaches in the past year, O'Brien's interest in the Knights job has caught the Roosters by surprise.

He was a critical member of Craig Bellamy's coaching staff at the Storm, spending 12 years at the club and ultimately running their attack.

O'Brien surprised Melbourne when he sought an early release from his contract following an approach from the Roosters, telling the Storm he wanted to learn under a different coach, in a different system.

Nobody fitted that better than Robinson, who is now a two-time premiership winner after his side beat the Storm in last year's grand final.

O'Brien also came to the Sydney glamour club following the endorsement of halfback Cooper Cronk, who had worked alongside him in Melbourne. He left the Storm with their blessing and was made a life member.

His impact at his new club has been there for all to see. The Roosters struggled with their attack last season and still won the competition. This year, they have scored more points than other team and are heavily favoured to become the first team since Wayne Bennett's Broncos in 1992-93 to win back-to-back titles.

In a short period of time, O'Brien has established a close relationship with the playing group and his departure - immediately or in the off-season - would be considered a blow to the organisation.

One of O'Brien's biggest supporters is former Knights five-eighth and Fox Sports personality Matty Johns, whose opinion is highly regarded at his former club.

"He's probably a little bit in between Michael Maguire and Anthony Seibold," Johns has said. "He's a first-grade coach waiting to happen."