Collingwood captain Darcy Moore won't face Adelaide after the star defender pulled up sore in his bid to return from a calf injury.
Saturday night's clash at the MCG had been earmarked as Moore's first match after suffering a calf strain in pre-season.
But in a hammer blow to Collingwood's hopes of containing a powerful Crows attack, Moore failed a fitness test at Thursday's training and was ruled out of the game.
"Darcy won't play," coach Craig McRae said.
"No, Darcy had to get through a fitness test and unfortunately he's pulled up a bit sore.
"I'm not sure exactly what that means at the moment, but he won't play."
The coach couldn't say for certain whether Moore's calf or another issue was the problem, or if it would sideline the 30-year-old beyond this week.
"I don't know. He left the track a little bit sore late and I haven't had a medical update yet," McRae said.
"It's probably too early to tell. He's out for now, and I'm sure if there's something more sinister we'll report that later.
"We planned this was the game (to return). He's done all the work, he's had four, five, six weeks of pre-season now and we've set that up, and again there's some reason that he's not there, and we'll get to the bottom of it."
The Crows are seeking a strong start to the new campaign after exiting last year's finals in straight sets, including suffering a loss to Collingwood in the qualifying final.
Adelaide spearhead Riley Thilthorpe is expected to be fit to play after dealing with back soreness through pre-season.
Thilthorpe, Darcy Fogarty and Taylor Walker pose a brutal challenge for the understrength Magpie defence.
"There's a lot of threats down there," McRae said.
"They've got three big targets and we'll have to plan accordingly.
"We survived last week without him (Moore) and we'll have to do something similar this week."
Collingwood conceded 63 inside-50s to St Kilda in opening round but won by 12 points.
McRae doesn't want his defence under that much pressure against a slick Adelaide outfit.
"The last 12 to 18 months, we've seen our backline be able to stack up when the odds are against them ... and we don't get the result without that," McRae said.
"But clearly we don't want that to be a pattern."
McRae remained confident Jeremy Howe was on track to return after next week's bye.
