Collingwood's injury woes have worsened after scans confirmed promising young defender Lachlan Keeffe will miss the rest of the season with a knee injury.
The 22-year-old suffered a torn anterior cruciate ligament in the Magpies' win against Adelaide on Saturday night and will undergo reconstructive surgery this week.
The incident appeared innocuous - he was battling for position in a marking contest against Crow Kurt Tippett before falling to the ground clutching his right knee early in the final term.
Keeffe is the fourth Collingwood player to suffer a serious ACL injury this year, joining Andrew Krakouer, Brent Macaffer and Luke Ball.
Other key defenders Ben Reid (thigh) and Chris Tarrant (calf) are also facing ongoing battles with injury, leaving the team's backline short of experience.
Collingwood football director Geoff Walsh said the injury was gut-wrenching for a player who had been a revelation in the early rounds.
"It's really disappointing for Lachlan and the club, especially considering he's been such a good contributor for us in 2012 so far," Walsh told the club's official website.
"He'll undergo a knee reconstruction and we expect him to be available to play early in the 2013 season."
The 204cm Queenslander made his debut against North Melbourne in Round 16 last season and played in four more matches for the season in both attack and defence.
He showcased his ability up forward when he booted three goals against Gold Coast in Round 18, but has held down a key defensive post with aplomb in 2012.
Collingwood host Greater Western Sydney this round before the following weekend's midseason break.