FREMANTLE coach Ross Lyon says he's keen to persist with the experiment of using young defender Alex Pearce as a key forward.

Pearce was thrust forward a fortnight ago to partner Matthew Pavlich in attack after Zac Clarke and Matt Taberner failed in the role.

The 20-year-old has managed just two goals in his two games since that time, but he has had seven shots on goal - giving Lyon optimism that better things are to come.

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"We've really liked it a lot," Lyon said of Pearce's move forward.

"We've gotten more flexible out of it.

"He's really quick, 196cm, and a really smart, young player.

"We're thrilled with him. He's another piece of the puzzle that helps us. It's been a real positive for us.

"We tend to keep him in the front half, because he puts on good pressure and is a viable marking option, and finding the ball a fair bit."

With skipper Matthew Pavlich battling an Achilles tendon problem, Pearce may have to carry a bigger load in Sunday's derby against West Coast at Domain Stadium.

Should Pavlich be ruled out, one of Taberner and Clarke will be a chance to earn a recall.

The make-up of Fremantle's defence is also up in the air this week.

Veteran backman Michael Johnson is ready to return from his hamstring injury, but Lyon is yet to decide whether it will be through the WAFL or senior ranks.

And Luke McPharlin faces a fitness test later this week after suffering a corked calf in the win over St Kilda. 

Lyon said his decision on Johnson would depend heavily on McPharlin's availability.