Captain Patrick Dangerfield will miss Geelong's game against Adelaide and could also sit out the Cats' bumper clash with Hawthorn after suffering a calf strain.
Elsewhere, Western Bulldogs stalwart Tom Liberatore will miss up to five weeks with a hamstring strain while Collingwood skipper Darcy Moore and fellow backman Jeremy Howe could return from injury against GWS.
Dangerfield, who turns 36 next month, pulled up sore from Geelong's comeback win over Fremantle and has been ruled out for at least a week after scans revealed a low-grade injury.
The explosive midfielder-forward will be a big loss against Adelaide on Thursday and potentially on Easter Monday against Hawthorn, who Dangerfield demolished in last year's preliminary final.
Dangerfield managed a calf complaint in pre-season and didn't play in the Cats' opening-round loss to Gold Coast.
"Pat reported some calf soreness following the match against Fremantle, with subsequent assessment and scans confirming a low-grade calf injury," Cats football boss Andrew Mackie said.
"Given Pat missed our opening-round game with a similar complaint, we'll take a cautious approach and get some loading into his training with his return to play at this stage earmarked for Easter Monday, or the week after."
The Bulldogs have the bye this weekend but Liberatore will miss at least their following clash with Essendon, and potentially more time after that, after suffering then playing through a low-grade hamstring injury against Adelaide.
"During the weekend's game, Tom developed some low-level hamstring tightness," Bulldogs medical boss Chris Bell said.
"Scans have since confirmed a low-grade hamstring injury.
"Tom won't play in the round-four game against the Bombers and we will work to confirm a return to play plan across the next period of time."
Moore and Howe both just need to prove their fitness at training to play at Marvel Stadium on Friday night.
GWS will be without defender Jack Buckley (concussion) but Toby Bedford (hamstring), Aaron Cadman (pelvis) and Brent Daniels (hamstring) could all push to return.
Sydney hope superstar Isaac Heeney recovers from his hamstring over their bye this weekend.
Brisbane key forward Logan Morris returns from a hand injury against St Kilda while Hugh McCluggage (calf) will push to play.
Saints defender Anthony Caminiti (hamstring) will miss four-to-six weeks.
Carlton will regain Adam Saad from a hamstring injury against Melbourne while Adam Cerra (hamstring) and Francis Evans (knee) will need to prove their fitness.
The Demons have lost key defender Daniel Turner (broken hand) for two-to-three weeks.
North Melbourne key defender Griffin Logue will miss two-to-three weeks with a low-grade hamstring strain.
