Will Ashcroft reckons he's near top form after a superb AFL finals debut further fuelled the Brisbane Lions' belief they can win the flag from fifth.

The midfielder was injured during the Lions' run to last year's grand final, the second-year talent only returning from a torn anterior cruciate ligament in the back half of this campaign.

"Shattered" not to be there in 2023, Ashcroft was quick to show what the team was missing on Saturday.

He carved up Carlton with a 20-disposal game that featured fast, clean hands and incisive link-up play through the centre of the Gabba.

"That's why you play footy, to play the finals and hopefully the grand final one day," Ashcroft told AAP post-game.

"Shattering last year ... but glad we ticked the first box ... and looking forward to what's ahead.

"Being out for 11, 12 months; you can't come back in and dominate from the get go.

"Nine home-and-away games set me up well and now I can start trying to get back to my best."

The Lions will play Greater Western Sydney in Saturday's semi-final, the prize an MCG preliminary final date with Geelong.

"We're excited, we're confident, we love the challenge," Ashcroft said.

"The hunger and the optimism that we can do it ... we've got belief right through our group, from leaders right down to the youngest player on the team."

Jack Payne's first-half knee injury is the main injury concern, the key defender understood to be a long shot to be fit for a duel with Giants gun Jesse Hogan despite Fagan's post-game optimism.

GWS made the most of Brisbane's inaccurate kicking to storm home and win at the Gabba last month and consolidate a top-four spot.

They were on the other end of a comeback on Saturday, run down by their Sydney rivals in a qualifying final thriller.

"What have we got to lose? If we can play the football we played, particularly in the first half tonight, we'll challenge anybody," Fagan said of the Giants clash.

"Everyone gets excited about the teams down the bottom of the eight that win and because the Giants lost everyone gets down on them and that's the narrative.

"They'll be determined to bounce back. We're going to have to play well to beat them at their ground."

The Blues narrowly avoided becoming the first team in AFL finals history to be scoreless at halftime, before kicking five straight goals to briefly offer hope of a miraculous comeback.

But Fagan didn't give much credence to Carlton's fightback after the Lions had booted the game's first nine goals and scored 60 unanswered points.

"There's momentum in footy ... what about all the goals we kicked," he said.

"We did a pretty good job in the latter part of the third quarter, just to crunch the game up, slow it down and be in a good position.

"I know the murmur went around, because it's happened a couple of times (this season).

"I don't think Carlton were ever going to get back into that game."