Adelaide moved to eighth on the A-League Men ladder and, with a game in hand against Central Coast, that is the worst they can finish. The top eight-placed ALM sides have direct entry into the Australia Cup.
"It had a lot riding on it this game. We knew that and we pushed the boys ... so I'm glad we got the points," Adelaide coach Carl Veart said.
The 33-year-old Ibusuki now has 15 goals for the season but his future is in limbo. He has been linked to a possible move to the Roar, who could do with his goal-poaching nous.
"Ibusuki has been around a long time in the A-League, so most of us know his exploits and what he is capable of," Roar coach Ruben Zadkovich said.
Ibusuki celebrates a goal against the Roar, who could be moved to sign him for next season. (Darren England/AAP PHOTOS)
"He is a top person and a top player. He is one of many strikers we are looking at and that process is only just getting started."
Veart said Adelaide would make a decision on Ibusuki and other off-contract players at the end of the season.
"He has done everything he can for us this season and we will make that decision after Wednesday's game," he said of the meeting with the Mariners.
Brisbane looked dead and buried when trailing 4-1 late on but roared home, with 19-year-old substitute Thomas Waddingham scoring in the 78th minute and winger Henry Hore notching his second goal five minutes later to set up a grandstand finish, before Adelaide held on.
The Roar, in ninth, had a dream start with a goal in the third minute to Hore, who went on a scything 30-metre run after a slick ball from midfielder Florin Berenguer.
Hore made his way into the box and unleashed a right-footer, with Adelaide keeper James Delianov making a mess of the attempted save.
Henry Hore was first to score for the Roar, his sixth goal of season 23-24. (Darren England/AAP PHOTOS)
The Roar had plenty of chances to add to their tally but the visitors equalised.
A slick ball into the box by Zach Clough was slotted home by Ibusuki in the 39th minute
Ibusuki was at it again in the 47th minute with a clinical header after silver service from Ryan Kitto, completing his second brace in as many weeks.
Panashe Madanha came off the bench for the visitors with a great run and delivery for Stefan Mauk to make it 3-1.
Madanha set up Harry Van Der Saag for Adelaide's fourth before the Roar scored two in quick succession.
The clash was the last for the Roar for captain Tom Aldred, who is yet to come to terms on a new deal for next season. Defender Kai Trewin is also unsigned and is reported to be in the sights of Melbourne City.
Roar goalkeeper Macklin Freke inked a new two-year extension during the week while versatile Antonee Burke-Gilroy signed on for one more season.
