ZAC CLARKE is in doubt for Saturday's Western Derby due to knee soreness.

The athletic ruckman damaged his right knee in a freak accident at a music festival on New Year's Eve.

Clarke slipped and injured his posterior cruciate ligament, which saw him miss all of the pre-season and the first three rounds of the home and away season.

Fremantle coach Ross Lyon said he was unsure if the current issue was related to that injury but admitted Clarke was in a race to be fit for Saturday's clash with West Coast.

"I couldn't say if it's related to that," Lyon said on Wednesday.

"He's got a bit of a sore knee though, so he's got to jump a few hurdles this week."

The Dockers do have options in the ruck department.

Jack Hannath played the first three rounds this year after playing 12 matches in 2013 and has been playing well recently in the WAFL.

Jonathon Griffin has fought his way back from a knee reconstruction and has been in tremendous touch for Peel Thunder, averaging 29 hit-outs in the last 10 matches, including 47 hit-outs last weekend.

The ruck duel will be pivotal on Saturday. Fremantle and West Coast are the number one and two ranked sides in the AFL for total hit-outs per game.

The Eagles have selection dilemmas of their own trying to fit Dean Cox back into the line-up after a two-week rest.

Lyon said he was wary of the Eagles tall timber in attack but will resist the temptation to bring veteran Luke McPharlin back early from his medial ligament strain.

"He (McPharlin) won't play," Lyon said.

"We thought he was a bit of a chance.

"We were quite optimistic on Sunday that he'd be right. He went backwards a little bit so we're aiming for Melbourne (next week) for him."

Matt de Boer is also a chance to come back from his knee injury this week, however it is unlikely to be in the AFL.

"He's running fit," Lyon said.

"He (de Boer) hasn't missed too much. He would be unlikely to come straight in. But who knows - if we lost a couple, he could. It's a nice position to be in."