Walters looked to have hurt his ankle in Saturday night's draw with the Sydney Swans at the SCG, limping off in the third term and taking no further part in the match.
Fremantle coach Ross Lyon said Walters would undergo all the usual scans in the days ahead, but conceded the prospects of Walters lining up against Melbourne at Patersons Stadium next week were not good.
"He will probably be unlikely this week," Lyon said.
"We are hopeful it is not too serious."
Lyon said he told the 22-year-old at the three-quarter time huddle no risks would be taken with the injury.
"I said, 'If you're not right mate, you do too much right for us - I'm not going to run you into the ground'," Lyon said.
"We were pretty keen to look after him and take no risk.
"He is really important to us."
Fremantle came into Saturday's match with key players Matthew Pavlich (Achilles), Stephen Hill (quad) and Aaron Sandilands (hamstring) already on the sidelines.
Moreover, Jonathon Griffin and Kepler Bradley were out for the season due to knee injuries.
Lyon said although the club has a lot of key position players missing, "most of our runners are there".
"When you can run and work you are going to be in games," Lyon said.
Lyon said Hayden Crozier, who was a late withdrawal from the game with a groin problem, should be OK to return next week.
The heavy injury toll was "just AFL footy", the Fremantle coach added.
"It is a high demand game, it is a brutal competition," Lyon said.
"We will just back the next person in."
