Fremantle are in the thick of the AFL top-four race but they are desperate to stay focused ahead of a western derby cash with West Coast.

Fremantle coach Justin Longmuir is urging his players not to get drawn into the lure of AFL finals talk ahead of a clash he rates as the club's most vital of the season.

Last week's 17-point win over the Western Bulldogs guaranteed the Dockers a first finals appearance since 2015.

Fremantle sit in sixth spot but they are still a chance to clinch a prized top-four berth if they can snare victories against West Coast and GWS.

The Dockers will start as raging hot favourites in Saturday night's western derby, and they will have the added motivation of the game being part of David Mundy's farewell.

Earlier this season, Longmuir felt his players got ahead of themselves as the external hype grew, and he doesn't want history to repeat.

"Come the end of the year there can be a lot of distractions and players can shift their mindset to outcomes and finals down the track," Longmuir said.

"I don't ban it (talking about top-four), I just try to make our players aware of where their minds can go and give them a fix of where to bring it back to.

"I don't know why everyone's talking about finals. We haven't spoken about finals.

"We don't talk about this week being a prelude to the finals. We talk about this being the most important game of the year.

"That's where our mindsets are."

West Coast enter the match missing 10 of their best 22 players, including Jeremy McGovern, Oscar Allen, Tim Kelly, Elliot Yeo, Willie Rioli, Tom Cole, Josh Kennedy, and Dom Sheed.

But one aspect playing in their favour is the forecast of up to 15mm of rain on Saturday.

The Dockers have struggled in the wet this season, and it's an obstacle they would love to overcome heading into the finals.

"It's a work in progress and we understand that as a club. We're not shying away from the wet conditions," Longmuir said.

"When we play our best footy it can handle wet weather conditions, so it's another good challenge for us this week."

How West Coast recover from last week's emotional send-off of Kennedy remains a big question.

"It's probably a good thing we're going into a derby," Eagles coach Adam Simpson said.

"Availability is probably our biggest issue. Can we be competitive and have a swing? You never know.

"A derby with a crowd, backs-to-the-wall situation for us. I'm just looking forward to seeing what the guys can bring."

Fremantle recalled fit-again goalsneak Sam Switkowski for the injured Matt Taberner (calf).

West Coast lost Kennedy (retired), Kelly (suspended), Rioli (personal reasons) and axed ruckman Bailey Williams.

Josh Rotham, Jackson Nelson, Hugh Dixon, and Rhett Bazzo come into the side.