Scans have revealed the 27-year-old injured the medial collateral ligament in his left knee during the Magpies' win over Richmond on Friday night.
Cameron joins Mason Cox (haematoma) and Aiden Begg (back) on the sidelines, after former first-choice ruckman Brodie Grundy was offloaded to Melbourne during the last trade period.
"We are all disappointed for Darcy, who at this stage will miss around six to eight weeks after he enjoyed such a strong start to this season," Magpies football manager Graham Wright said.
"Darcy is an absolute professional who we know will be dedicated in his approach to his rehabilitation and we expect to see him return to the senior side in the second half of the season."
Collingwood are yet to put a timeline on Cox's return, while third-string ruckman Begg is at least a month away from playing.
"We've had a bad week in the ruck stakes," Collingwood coach Craig McRae said on Friday night.
"We've lost Mason for a period of time and now it looks like Darcy will be out for a significant period."
While Grundy is handling Melbourne's ruck burden following Max Gawn's knee injury, the Magpies will have to contemplate their next move after nine-game tall Ash Johnson chipped in against Richmond.
Versatile tall Nathan Kreuger (shoulder) is also sidelined until the second half of the season, while defender Billy Frampton, who shut down Tigers forward Tom Lynch, started his career as a ruckman and could be another option
"I half-joked with Jamie (Elliott, a 177cm forward) that he might be rucking next week," McRae said.
"I don't know. Funnily enough, we talked about this before the game, around 'what-ifs', if Darcy went down.
"So we've got a few things up our sleeve but it's a shame.
"Aiden Begg's not fit and available, he's probably a month away himself. He's got his own issues at the moment.
"We might have to be a little bit creative, we'll wait and see."
McRae played down suggestions of turning to 19-year-old pre-season pick-up Oscar Steene.
"I'm rapt with how he's developing," the second-year coach said.
"It's not impossible but I want to set players up to succeed and it might be a bit early for him."
Meanwhile, Jack Ginnivan will return from his suspension for drug use through the VFL on Saturday night.
McRae is confident he could squeeze Ginnivan, Bobby Hill and Beau McCreery into the same forward line when the 20-year-old is ready to return.
"You've got to warrant the opportunity and I'm looking forward to seeing how he goes," McRae said.
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