FREMANTLE coach Mark Harvey will encourage ruckman Aaron Sandilands to play an attacking game in Saturday's western derby to counter in-form West Coast ruckman Dean Cox.

After a defensively minded start to the season, Cox has been pushing forward in recent weeks, sending the ball inside 50 13 times in his last three games.

Harvey said Sandilands would have to play a similar role to make the All-Australian ruckman accountable.

"Dean plays a unique way in the ruck, the way he runs and ends up finishing with the ball – he does get a lot of possessions," Harvey said on Friday.

"Aaron's got to be able to try to say, 'well okay, you want to go that way, you better think about coming my way.'

"I think Aaron had three or four shots on goal last week. That'd be enough for Dean to start thinking."

Another key match up will be Ryan Crowley and whichever West Coast midfielder he is assigned to.

Past derbies point to a feisty encounter with Daniel Kerr but Harvey wouldn't give anything away, suggesting Andrew Embley was a possible match-up for his chief tagger.

Crowley said his role would be tough no matter who he ran with.

"The Eagles have got a few good movers through the midfield (so) I'm not sure who I'll get yet, but I'm sure whoever I get will be a big challenge," he said.

"I think having a role gives you that bit of direction.

"You know where your starting points are and where to go from there. So I suppose I do (prefer having a role)."

Crowley said young players Nic Suban, Stephen Hill and debutant Matt de Boer were all capable of overcoming the occasion in their first derby.

Harvey agreed, and said he would throw a few of his young players into the game from the first bounce to get them involved early.

"In a football aspect they need to grow up quickly," he said.

"That's always interesting and how they handle that. I just said, 'Make sure you're exciting your more experienced teammates'.

"In a game like this, this is where you want to see them really excel. Just to see them being able to hold their own."

West Coast dropped premiership tagger Tyson Stenglein for the clash and will play a first gamer of its own in Adam Cockie.

Harvey said his counterpart John Worsfold may have been sending a message to his senior players.

"Sometimes you need to make a change and make sure that your older players understand that they're not necessarily an automatic selection," the coach said.

"That may well be the reason why they've decided to drop a guy like Tyson.

"Young Cockie is a well-built player himself, and he's been around a number of years in the WAFL system."