Brisbane ruckman Oscar McInerney will be the heartbreak story of the Lions' second grand final appearance in as many years after dislocating his shoulder.

McInerney was helped from the field late in the first quarter of the Lions' preliminary final win against Geelong on Saturday cradling his left shoulder after it popped out.

The 30-year-old attempted to tackle Cats midfielder Tom Atkins but hurt his shoulder in the process.

McInerney strapped up his shoulder and bravely played on until early in the third quarter.

But he was forced off the field again when his shoulder gave way for a second time.

During the last quarter, McInerney was taken to hospital in an ambulance for further assessment.

The Lions hung on to win an epic preliminary final by 10 points and progress to the decider again, 12 months after they fell four points short against Collingwood.

Brisbane will be aiming for their first premiership since 2003.

"I probably reckon when you've double dislocated your shoulder in a preliminary final, you're not going to be playing in the grand final," Lions coach Chris Fagan said of McInerney.

"Knowing Oscar, he would have hoped that if he could get through this game, that he'd be right to get through the game again next week

"He's just been so enormous for us.

"His growth as a leader, from where he was five or six years ago, to where he is now and what he means to the team … it's just such a real pity."

Fagan praised McInerney's commitment to returning to the ground after he was injured initially.

"He's full of heart, and he's a bloke that just gives himself to the team," he said.

"That's why he's admired so much.

"So it'll be a downer for us that he can't play in the grand final, but I know the boys will probably find a way to use that as a dedication for the game as well."

Star forward Joe Daniher, the hero in the Lions' stunning come-from-behind win against GWS last week, was forced to take on the No.1 ruck duties when McInerney went down.

Rather than use Daniher as the main ruck again in the grand final, Brisbane would likely recall Darcy Fort, who has played just two games this year, or four-gamer Henry Smith.

Fort or Smith, with back-up from Daniher, will face a huge task coming up against Sydney big man Brodie Grundy.

Conor McKenna was subbed into the match for McInerney during the third quarter on Saturday night.

AAP