Fremantle coach Ross Lyon is optimistic Michael Walters has avoided serious injury despite the star goalsneak damaging his troublesome left knee in Sunday's eight-point western derby loss to West Coast.
Walters suffered the injury in the first quarter while battling Eagles defender Brad Sheppard for a loose ball, with his knee crashing into the Optus Stadium turf in their duel.
He suffered a PCL injury late last season to the same knee.
Walters returned to the field early in the second quarter, but was still clearly affected by the injury and promptly returned to the bench in his final act of the day.
West Coast trailed by 20 points at quarter-time, but three goals each to Jack Darling and Josh Kennedy helped lift the Eagles to the 13.11 (89) to 12.9 (81) victory in front of 56,521 fans.
It was their sixth derby win in a row.
Eagles captain Shannon Hurn (30 disposals) and Dockers midfielder Lachie Neale (35 disposals) were tied winners of the Ross Glendinning medal as best afield.
Lyon said the initial prognosis on Walters wasn't too bad.
"I think it's a low-grade medial," Lyon said.
"It might be a half grade, where he might be able to come up (next week). But if it's a grade one, you're probably looking at four weeks.
"So that's frustrating, because he was looking quite dangerous."
Fremantle were lucky to lead 27-7 at quarter time after losing the inside 50m battle 17-7.
Darling booted three goals in the second term to propel West Coast into the lead, and the Eagles held on from that point as the match turned into a titanic arm wrestle.
Tensions were frayed between the two clubs earlier in the week when Fremantle threatened to scrap the Ross Glendinning medal.
But a compromise was eventually reached, with the name of a past Dockers great to be added to the medal in time for the round-20 western derby.
Lyon could see the irony in Sunday's medal winner being a tied affair between both sides.
Eagles coach Adam Simpson was happy with his team's performance against Fremantle, but he felt they missed some clutch goals at crucial times.
It came a week after West Coast booted 10.19 in last week's 10-point win over Carlton.
"We did miss a few easy ones today. That's two weeks in a row now that could have possibly hurt us," Simpson said.
"Luckily it wasn't for a loss. We were close to most accurate team in the comp in the first four weeks, then the last couple of weeks, while it wasn't epidemic today, (there were) a couple of misses.
"But then (there was) a couple of good clutch goals from out leaders and good players."
West Coast (5-1) are only percentage behind ladder-leading Richmond following five straight wins.