Fremantle coach Justin Longmuir is hopeful skipper Nat Fyfe will return before the mid-season bye, but small forward Lachie Schultz has become the latest Docker to enter the AFL's health and safety protocols.
Fyfe, who underwent a shoulder reconstruction during the off-season, is still sidelined after having back surgery last month.
Fremantle is unsure exactly when Fyfe will return, but the round 12 home clash with Brisbane is looming as a possibility.
"We hope to see Nat back a couple of weeks before the mid-season bye," Longmuir said on Thursday.
"It's hard to put an exact time frame on his injury, but he's progressing really well."
Earlier this week, Longmuir rejected claims Fyfe should hand over the captaincy, saying the 30-year-old has been critical in nurturing the club's next batch of leaders.
Schultz will miss Sunday's clash with Essendon at Marvel Stadium after being forced into the health and safety protocols.
He joins David Mundy and Brennan Cox as others to have entered protocols this season, while Longmuir himself missed the past two matches after contracting COVID-19.
Longmuir is confident key defender Alex Pearce (ankle), Darcy Tucker (concussion), and Caleb Serong (knee) will all be available for selection.
"I know Alex has some pain in the front of his ankle joint," Longmuir said.
"These things can get to 85 or 90 per cent right really quickly.
"It's that last 10 per cent that can take a bit of time. We think it's improved, but we want to make sure he's 100 per cent.
"We're really confident he will get up for this weekend, and if that's not the case, then he is a certain starter next week."
Essendon star Jake Stringer will miss a second straight match with a hamstring injury, but the Bombers are set to regain Tom Cutler (protocols) and Nik Cox (ankle).
Fremantle are 3-1 following a strong start to the season, while Essendon (1-3) broke through for their first win of the campaign last week with a tense four-point triumph over Adelaide.
