Fremantle is expecting to be without Michael Walters for at least four weeks after the star forward suffered a grade one medial ligament injury against West Coast at Optus Stadium on Sunday.
Walters injured his heavily strapped left knee just before quarter-time during Freo's eight-point loss to their cross-town rivals - West Coast's sixth consecutive derby win.
The lively forward twisted his knee during a one-on-one contest with Brad Sheppard in the Fremantle Dockers' forward 50, before Brandon Matera swooped on the loose ball for a classy goal.
Walters stayed on the field briefly in an attempt to shake off the injury, but eventually hobbled to the boundary line for assessment.
The 27-year-old looked dejected talking to the club doctor and left for the change rooms at quarter-time, shaking his head.
He returned to the field early in the second term and lined up at full-forward but lasted barely a minute before hobbling off for good.
"I think it's a low-grade medial," Fremantle coach Ross Lyon said post-match.
"He tried to run with it (and) couldn't quite move so hopefully when it cools down it's only a grade one.
"Our doctors made a call but he couldn't get moving so we will see what the week brings but it doesn't look great.
"We've had a grade two medial recently with Stef Giro that was six weeks.
"It might be a half grade and he might be able to come up but if it's a grade one you're looking at four weeks."
Walters suffered a PCL injury to the same knee in round 18 last year against Hawthorn, and was sidelined for the remainder of the year and the start of Fremantle's pre-season.
His absence compounds the loss of improved key forward Matt Taberner, who will miss a significant amount of football with a foot injury suffered against the Western Bulldogs last Saturday.
Lyon said the loss of Walters hurt, but ultimately his side failed to match West Coast's hardness in key moments.
"It's not ideal but we had enough opportunities," he said.
"I thought they were harder overall - not dramatically, but just in a few clinches.
"We'd like to be harder for a bit longer."
Lyon all but declared Aaron Sandilands a certain starter against Richmond next week, despite talk of the veteran ruckman being rested.
Scott Jones was named an emergency for Sunday's match but will likely need more time in the WAFL before making his AFL debut.
"If he can hang on for a little while then we'll look to give him a rest," Lyon said of Sandilands.
"(Scott) Jones and (Lloyd) Meek have got a bit of work to do.
"Sean Darcy is still a long way from coming back.
"(Michael) Apeness came back today (for Peel Thunder) - he probably needs a couple more."
Lyon also indicated the club's raft of inexperienced players were handling the demands of AFL football well, and would be rested during the week rather than on game day.
