Fremantle’s challenge of taking on in-form Collingwood just got tougher after Ross Lyon ruled veteran ruckman Aaron Sandilands out of the MCG clash.

Speaking on 6PR radio on Tuesday night, Lyon declared the influential 211cm big man was unfit to take on the Pies.

Sandilands suffered concussion after a heavy head clash with North Melbourne youngster Sam Durdin in Sunday's 28-point loss.

It is unclear how long the 35-year-old will be sidelined but the Dockers have been keen to give him a rest after playing every game so far in 2018.

"He's not in great shape. He's a bit sore and sorry for himself today, so he definitely won't play this week," Lyon told 6PR.

"And then he's been such a great warrior for us that we'll be conservative with him and give him every chance to come back healthy."

Sandilands' withdrawal opens the door for Michael Apeness to possibly play his eighth senior game after being drafted with pick 17 in 2013.

Apeness has been riddled with knee issues at the Dockers and also battled a broken collarbone, but has strung together the past four WAFL games as Peel's lead ruckman.

The 23-year-old is averaging 30 hit-outs, 12 disposals and a goal over the past month and shapes as the likely inclusion ahead of untried teammates for the big job on Pies tall Brodie Grundy.

"We're fortunate, in a sense, that Michael Apeness, Luke Strnadica and Jonesy (Scott Jones) and Lloyd Meek are all available," Lyon said.

"Michael Apeness has had a horrific run with injury over the last four years but he's starting to get a little bit of continuity and the other boys are whacking away.

"We'll have to do it through match committee, but there's probably a few line-ball decisions there."

While many Fremantle fans hoped Apeness could develop into a key forward, his future appears to be in the ruck.

"The reality is he's 200cm, and his size and shape and mobility, he's really a ruckman that might be able to push forward," Lyon said.

"He was really never going to be a key forward, we wouldn't have thought, and I think he likes the ruck and sees that as his best position, so that's where we're grooming him.

"He's been here a while now but he's just had a horrendous run."