Matthew Scharenberg will need his third knee reconstruction, continuing his cursed run of injuries and adding to Collingwood's appalling AFL misfortune.
The 22-year-old defender hobbled off with a left knee injury in the third quarter of Saturday's 28-point loss to Richmond at the MCG.
Scharenberg overcame foot injuries before needing a left reconstruction in 2014 and another the following year on his right.
"We fear the worst, which is shattering for him - that's the overwhelming feeling in the rooms at the moment, is disappointment for him," Collingwood coach Nathan Buckley said.
"He's shattered - he's a young bloke who loves his footy and he's been through his fair share, with his feet and then his ACLs.
"There's not a lot of light at the end of the tunnel right now for him. He's shattered, he's not in a great spot."
But Buckley praised Scharenberg's character and said the club would support the player as best they could.
He said Scharenberg had family across from SA to watch the game.
Collingwood are in the top four despite a woeful run of injuries this season.
In the past few weeks, they have lost backman Linden Dunn to a knee reconstruction, and top midfielder Adam Treloar might not play again this season because of hamstring surgery.
In-form forward Jordan De Goey also was sidelined this week because of a leg injury.
With Scharenberg out of action, Collingwood will hope fellow defender Tyson Goldsack can continue his speedy recovery from a pre-season knee reconstruction.
Remarkably, Goldsack might return before the end of this season.
"There are still a lot of ifs that we really can't be sure of, that we can't be sure about," Buckley said.
"Goldy ... is really bullish, he's training really well."
Fellow defender Jeremy Howe was also knocked out in the first quarter on Saturday and Scharenberg limped off in the third, leaving them two men down on the bench.
