WEST Coast is prepared for a "hostile environment" in Fremantle's first home Western Derby since last year's infamous round 20 clash, but coach Adam Simpson has bigger things weighing on his mind trying to keep emerging tall Oscar Allen in the side.

The Eagles are set to retain Tom Hickey as Nic Naitanui's ruck sidekick, with the Dockers likely to play at least two, and possibly all three, of Aaron Sandilands, Rory Lobb and Sean Darcy.

But Simpson isn't wedded to the duo, who are an imperfect fit given they don't spend significant time forward and neither played 60 per cent game time in last round's tense win over Hawthorn.

Nathan Vardy's ordinary form has created a dilemma for the Eagles. Pic: AFL Photos

West Coast's dilemma is compounded by Nathan Vardy's ordinary form this year, and the premiership tall will be sidelined by a knee problem for the next two weeks.

Allen was shifted to defence in last round's victory over Hawthorn, but with key backmen Tom Barrass (calf) and Jeremy McGovern (suspension) due back the Eagles are facing some selection headaches.

"We've still got to work through what we're going to do with Nic and obviously Hickey's form on the weekend was pretty good," Simpson said.

"We haven't quite settled with how it's going to look with Nic in the side. Ideally, it's a forward-ruck that complements Nic's output."

Asking Allen, who stands just 192cm and is only in his second year, to spend more time in the ruck shapes as one of the reigning premiers' issues on the run home as they try to settle on a line-up before finals.

"That's what we've got to explore. We've got to find out one day what he can do," Simpson said.

"To get him to ruck 50 minutes is a challenge, but if anyone can do it he probably could at the moment.

"He's the type of player that will do whatever it takes for the side."

The Eagles can keep the pressure on Collingwood, who they host next round, in the race for second spot with a record-equalling ninth-straight victory over Fremantle.

"This is the only record I'm aware of, because everyone tells me," Simpson said.

"Obviously, we've had a good run, but that doesn't mean anything.

"Both teams are pretty even. When you look at the numbers, there's not many stats we're in front of Fremantle at the moment.

"But we still think our best is as good as anyone's, so we plan on playing at our best."

Dockers coach Ross Lyon wasn't interested in "regurgitating" the Andrew Gaff and Andrew Brayshaw incident from last year, except to call on supporters to be passionate "about our club and our performance", and Simpson was also ready to leave it behind after Saturday night.

"We're anticipating a hostile environment from a crowd point-of-view, but that's no different (to a normal 'away' derby)," Simpson said.

"This is probably the last chapter in the story, isn't it? We get through this game and we move on."