Collingwood will be without Steele Sidebottom for around six weeks after the Magpie suffered a knee injury in Round 11's win over North Melbourne.
Sidebottom was substituted early in his milestone 300th game at Marvel Stadium after suffering the knee injury, with scans now confirming he has suffered a medial collateral ligament sprain.
The club confirmed on Wednesday that the timeline for Sidebottom's return was around 6-8 weeks.
Elsewhere at the Pies, Billy Frampton is nearing a return from a groin injury after being sidelined since Round 8. Collingwood is expecting the 26-year-old to be available for selection should he get through training this week.
Reef McInnes has also been cleared of serious injury after hyperextending his knee during the VFL. After undergoing scans, the club is confident the 20-year-old remains in the selection conversation if he makes it through training and testing throughout the week.
Speaking to media on Wednesday, assistant coach Justin Leppitsch confirmed Jamie Elliott also won't feature this week as the Pies head to Perth due to a shoulder injury.
Patrick Lipinski (shoulder) and Dan McStay (finger) are on track to return in Round 13's King's Birthday clash, continuing to progress steadily through their respective recoveries.
The Pies, who have banked seven consecutive wins, sit atop the ladder as they take on the struggling Eagles in Round 12.