Central Coast chairman Richard Peil has quit, declaring A-League funding cuts have made it "extremely financially challenging for small clubs to survive".
Mike Charlesworth sold the Mariners to Anytime Fitness co-founder Peil in 2022, triggering a remarkable turnaround for the club.
The Mariners were crowned A-League Men (ALM) premiers and champions earlier this year, also winning the AFC Cup, while they returned to the national women's competition after a long absence.
But Peil's pulling of the pin, six days out from his Mariners hosting the ALM season opener, raises fresh questions about the long-term future of the league's smallest club.
"It is with deep sadness that I announce I have handed the operations and funding of the Central Coast Mariners back to Mike Charlesworth, effective from today," Peil wrote in a statement published on Saturday.
"When I took over the club, funding from the APL (Australian Professional Leagues) was $2.35M per year. This was reduced to $2M last season, and now for this season has gone down to just $530k.
"This drastic slashing has made it tough for me to improve the financial performance of the club to a position that's sustainable for me to continue to fund solely by myself.
"It has also made it impossible for me to achieve the 'milestones' Mike and I agreed on nearly three years ago, that would have given me the right to purchase 50 per cent of the club at the end of the coming season.
"It has become extremely financially challenging for small clubs to survive following the recent cuts to funding."
Peil signed off his note, on the Mariners' club website, by thanking fans and his "children Jack, Toby and Tayla for allowing me to spend close to $7 million dollars of their inheritance".
Charlesworth's reign was marred by four wooden spoons in the space of five ALM seasons, the bizarre and brutal failure that was Usain Bolt's trial, and criticism from fans for the club's bare-bones budget.
It is unclear what Charlesworth, who tried to offload the club for multiple years before striking his multi-year deal with Peil, now has planned for the Mariners.
"I'd like to sincerely thank Mike and his team for the support and cooperation in making this transition as smooth as possible. I sincerely wish Mike and all involved at the club the very best for the year ahead," Peil wrote.
The APL made mass redundancies in January then told clubs in July there would be a savage cut to the central distribution pot.
APL chair Stephen Conroy, speaking when 2024/25 cuts were confirmed, insisted no club would have an issue meeting the leagues' salary floor.
Peil's public resignation note praised Conroy and Macarthur FC chair Gino Marra for doing "an incredible job fighting to restore the A-Leagues".
"I believe they will get there. However, it's not going to get there in a timeline that my financial position can accommodate," he wrote.