Bulli are out of the Illawarra Premier League finals picture, following a difficult campaign launched without several of key players, including Guy Knight and Harry Callahan, who won the NSW NPL premiers trophy with Wollongong Wolves on Sunday.

In a thrilling grand final, Knight sealed a league and grand final double for Bulli with a header in injury time to seal a 3-2 win over Wollongong United, having let a two-goal advantage slip in the second half.

"It is an unbelievable feeling," Bailey said after the grand final.

"This group is second to none. We have desired and craved this grand final for a number of years and today we have done it.

"We are going to celebrate this like we haven't celebrated anything before."

The Mercury unsuccessfully attempted to contact Bailey on Monday.

It's understood Bailey intended to see out the season as recently as a fortnight ago and that the club has already approached at least one candidate to take over next year.

However, Bulli president Paul Connery is adamant there was no ill-feeling.

"We wish him all the best," Connery said.

"Matt was going to stand down at the end of the season anyway, but he thought the time was right now and we respect that.

"He'll always be highly regarded by everyone at the club, especially for what we were able to achieve last year.

"Obviously it's been difficult this year, just with the number of players we've lost and the changes we've had to make. We'll prepare as well as we can for the final and hopefully be able to come away with a trophy."

Bailey's departure came after a 2-1 loss to Olympic, who they will meet again in the Bampton Cup final at JJ Kelly Park.

Bulli led, before Jamie Wakeling equalised and Mark Every scored the winner in injury time, which secured Olympic's premiers title with two rounds remaining.

The Cup final will be played on Saturday at JJ Kelly Park, 24 hours before the Wollongong Wolves' final home game against Marconi at WIN Stadium, where they will lift the NSW NPL trophy.