The Lions have been dealt a huge blow ahead of Saturday night's match against Fremantle with ruckman Mitch Clark being ruled out with a groin injury. 

Clark failed to complete Friday's closed training session which prompted the Club to withdraw him from the team.

He has been replaced in the Lions' side by Cheynee Stiller.

Clark's absence will certainly be felt, particularly considering the current form of All-Australian Fremantle ruckman Aaron Sandilands - leaving Matthew Leuenberger to fend against the Docker giant

"Mitch hurt his groin at training today and is out of the team,” Lions Senior Coach Michael Voss said during today's joint media conference with Dockers Coach Mark Harvey at the Gabba.

"It means another big job for Matty Leuenberger who will come up against Sandilands who is in red hot form."

"That will be a nice challenge for one of our younger players," he said.

Key defenders Matt Maguire and Daniel Merrett - who would normally be first in line to relieve Leuenberger in the ruck - will also be sitting on the sidelines leaving potentially only Jared Brennan to support in the ruck.

"[Leuenberger] has been good. He has been moving around a lot. He pretty much missed all of last year and it will be worthwhile for him to get a number of games under his belt,” Voss said.

"We would love to be able to have our ruck combination there, but it is not. So he is going to have a really hard task playing against an All Australian ruckman."