Lenny Harbinson has resigned as St Gall's manager after he said the post has "become increasingly untenable".
Harbinson, who took charge of Antrim's top club in 2009, claims he did not receive sufficient support from the club's committee.
"It is highly unlikely our ambitions will receive the necessary support from our internal adminsitration," he told the Irish News.
Harbinson guided the west Belfast club to the All-Ireland title in 2010.
St Gall's have also won the Antrim club title in 10 of the past 11 years.
"We appreciate that it's been a difficult two years and frustrations can sometimes get the better of the individual," said the St Gall's committee.
"We wish Lenny, like all past team managers, every success in the future."