Clouds were gathering ominously above Castle's Pyrmont apartment on Thursday as speculation mounted she had less than a week left in the top job.

She was a late scratching from a crucial meeting with the state chairmen to go over RA's 2019 balance sheet and cash position.

Less than 24 hours earlier, Castle's fellow directors excluded her from a board conference call on Wednesday night. She was unaware the meeting had taken place.

Castle's withdrawal from Thursday's balance sheet meeting was unexpected and unexplained to those present on the call, with chief financial officer Simon Rabbitt and new director Peter Wiggs left to steer the talks, which were the first opportunity for the Super Rugby chairs to size up RA's full financial picture.

The developments came as a board source told the Herald Castle would not see out next week at the helm of the business after losing the confidence of the board.

The 48-year-old was not aware of any threat to her job when contacted through a spokesman. Indeed, she was scheduled to appear on the ABC's 7.30 current affairs program on Thursday night, recording an interview with presenter Leigh Sales earlier in the day.

The biggest question the RA board will have to answer is who will replace her.

There do not appear to be any internal candidates of sufficient experience or standing to fill the role, leaving the likely scenario that a director would be asked to step up in an interim capacity. Wiggs and World Cup-winning Wallaby Daniel Herbert would be the most qualified.

Wiggs runs private equity firm Archer Capital and is chair of Supercars after Archer bought the business for a reported $180 million from SEL in 2011. It is now reportedly worth about half its purchase price and is in the middle of difficult broadcast negotiations to renew its deal with Fox Sports and Ten.

Herbert is highly regarded in the game and is the most experienced sports administrator on the board, having served as Queensland Rugby Union executive general manager and chief commercial officer, among other roles, over an eight-year period. He is now chief executive officer of strata management firm SSKB.

Outside the current board and administration, both Phil Kearns and Nick Farr-Jones have been touted as would-be successors, although the board would come in for fierce criticism if it made a permanent appointment without following a formal and independent recruitment process.

Farr-Jones told the Herald's CBD column on Wednesday that he "would like the challenge, but I really like what I'm doing at the moment".

His involvement in a funding scandal while chairman of the NSW Rugby Union would likely come up for discussion. Farr-Jones used $56,000 of NSWRU money earmarked for Indigenous education to dole out a secret personal loan to former Wallaby Jim Williams in 2015. It was not paid back until some six months later. A federal government investigation cleared the World Cup-winning former captain of misusing federal funds.

Kearns lost out to Castle when both applied to replace Pulver in 2017. He has been coy on whether he would throw his hat in the ring again, answering a direct question on the matter from Fox Sports this week with references to his contribution to the grassroots.

Farr-Jones and Kearns led the charge this week on the explosive letter signed by 10 Wallabies captains and sent to interim chair Paul McLean. The letter calls for the current administration to step aside and for a special general meeting of the RA members to be convened by the end of the month.

Farr-Jones told CBD he met with McLean on Thursday. "I had good discussions with Paul McLean today and we're trying to work amicably to achieve the required outcome for the benefit of the game," he said.