When a frustrated Paul Okon walked out on Tuesday afternoon from the Mariners' Gosford headquarters, he left behind an A-League club facing many of the same issues that had plagued them for three years.

Unlike Tony Walmsley before him, Okon wasn't sacked.

He'd only met management on Tuesday to discuss a contract extension and plans for next season.

But a disagreement over what the club labelled "strategic direction" - believed to involve less control for Okon over recruitment - led to the 45-year-old quitting with immediate effect.

The Mariners' long-standing issues are again in sharp focus, as they embark on the final four rounds without their head coach and assistant Ivan Jolic, who has followed Okon out the door.

Potential successors must be sussed out - and suitors must decide whether they have the stomach to work with the club's paltry budget.

Already, there are links to former Newcastle coach Scott Miller, ex-Melbourne City assistant coach Michael Valkanis and Olyroos coach Aurelio Vidmar.

Until then, youth mentor Wayne O'Sullivan will take the reins as caretaker and attempt to avoid the wooden spoon that had marked the end of the Walmsley era in 2016.

That was all supposed to change when Okon, a youth development expert with Young Socceroos and Olyroos pedigree, arrived with a mandate to get the best out of a young playing group at a cash-strapped club.

With mere weeks to prepare a largely inherited squad, the 45-year-old steered the Mariners to eighth place in 2016-17.

With a full pre-season and freedom to recruit his own team, this campaign started so promisingly the Mariners even reached a mid-season top-four placing for the first time since near the end of the club's golden era.

But a lack of depth, particularly in the front third, yielded an equal league-low 25 goals and an 11-game winless run.

Sunday's 5-2 loss to Melbourne Victory leaves them three points off bottom place.

Okon and Mariners chief executive Shaun Mielekamp were not available for comment on Tuesday, but the club issued a statement.

"Both Paul Okon and the Central Coast Mariners have been in discussions for several weeks about the strategic direction of the football club," it read.

"Given the club's future strategies and plans, both parties have agreed that it is best to end the association immediately to give the club an opportunity during this vital period to re-sign players and target new players."

Okon wished the club the best for the future.

"I will forever be grateful to the Mariners for the opportunity they gave me," the statement said.

"I thank the players for their commitment and the fans for their support."

Okon's name is one of a number linked to the Sydney FC job, which will be vacated at season's end when Graham Arnold takes charge of the Socceroos.

Australian Associated Press