The Sea Eagles lost their last seven games of the 2022 season as the club's decision to wear a one-off pride jersey divided and thwarted a playing group that had made the top four the campaign before.
Hasler had a year to run on his contract but his position first came under scrutiny when Manly missed the finals series, meaning the coach failed to satisfy a clause in his contract that would have triggered an automatic extension for 2024.
The situation reached critical mass this week when chairman Scott Penn claimed this week the Sea Eagles needed a football department fit for its "premiership-winning team".
In plotting a succession plan, Penn favoured ex-South Sydney and Brisbane coach Seibold, who was previously an assistant on the Manly coaching staff.
As recently as Wednesday night, Hasler was reported to have told the Sea Eagles he was open to having Seibold as an assistant in 2023 with the view to vacating the head coaching role at the end of that season.
But after meeting on Thursday morning, the board determined the regeneration would be fast-tracked as the embattled club hopes to once-and-for-all mend the divides that cruelled their latest campaign.
Hasler's exit could yet have a ripple effect on the playing group, key members of which have voiced their concerns about their off-season turmoil.
Captain Daly Cherry-Evans is famously close with the ousted coach as it was Hasler who handed the halfback his NRL debut in 2011 and developed him into a premiership-winning playmaker by the end of the year.
Just last month, Cherry-Evans admitted he had contemplated leaving the club amid a week of rumours around his relationships with other players.
Tom and Jake Trbojevic's management have also claimed the pair are concerned about the instability at the club.
Both are also tight with Hasler and share the same management company.
The Sea Eagles could ill-afford to lose the pair, one a Dally M Medal-winning fullback and the other a 15-time State of Origin representative forward.
Hasler is the most recent coach to taken Manly to the premiership, doing so in 2008 and 2011, before leaving the club for a stint at Canterbury.
After two grand-final losses with the Bulldogs, Hasler returned to Brookvale in 2019 to become the second-most capped coach in the club's history behind Bob Fulton.
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