Brisbane Lions coach Chris Fagan has issued his troops a brutal reality check ahead of Friday night's crunch AFL semi-final against Melbourne.

The Lions go into the MCG blockbuster as underdogs, having lost their previous two matches against the defending premiers this season.

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Fagan has branded both those performances "unacceptable" from his men, and insists the Lions are raring to set things right on Friday night.

"The bottom line against Melbourne is that we have played with unacceptable effort and attitude and we have to change that around," Fagan said.

"There is nothing else to talk about. Mindset is a key thing in every game, particularly in finals.

"Melbourne are the only team this year that have caused us some problems. We've recognised that and we have got to change that.

The Sydney Swans provided the Lions with a blueprint on how to beat the deadly Demons, and Fagan is hoping his side can also expose flaws in Melbourne's game.

The Brisbane boss admits his players have been buoyed by their thrilling two-point win over Richmond in last week's elimination final at the Gabba.

However, the 61-year-old knows a much sterner test will come on Friday night, against a Demons side that thumped them by 58 points just three weeks ago.

"What hopefully you will see is a much better effort than what we have produced the last couple of times we've played them," Fagan added.

"I feel confident in our group. Last week was a tremendous win and gave us a fair bit of belief.

"We have won five of our last seven games so our form is not too bad, other than the Melbourne loss."

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Fagan is remaining tight-lipped about the makeup of his side but has Cam Rayner and Noah Answerth available after both served suspensions last week.

Oscar McInerney is out with concussion, with Fagan talking up experienced ruckman Darcy Fort as his likely replacement.

"One of the reasons we brought Darcy to the club was because we thought Oscar needed some back-up, and as it has turned out we've needed that in a final. It is good to have him," Fagan said.

"Oscar missed a game against the Giants a few weeks back with Covid and Darcy came in and was one of our best players. We have a lot of faith and trust in him."

Fagan said when Melbourne lost last week to Sydney - setting up Friday's clash with the Lions - he saw it as "a great opportunity" rather than a 'here-we-go-again' scenario.

"If you want to be the best you've got to beat the best," he said.

"We haven't beaten them the last four times, but prior to that we did beat them. The good thing is that we played them a couple of weeks ago and we learnt a lot.

"We had similar experiences against Richmond. I think they won 15 in a row, which is more than four in a row. We had to find a way to overcome how they went about things.

"I don't see this is any different as a task. We have to be as strong mentally as they are."

with AAP

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