Maynard has avoided any structural damage to his left knee, but coach Craig McRae on Tuesday confirmed he will miss three to four weeks.
That rules the hard-nosed backman out of Thursday night's blockbuster against Geelong, games against West Coast and Hawthorn and leaves him in a race against time to face reigning premiers the Brisbane Lions.
"No, 'Bruzzy' won't play. He's having a minor procedure in the next day or so," McRae said.
"... He'll miss three to four weeks."
Collingwood later confirmed Maynard would undergo a minor procedure to his pes anserinus - the conjoined tendons of three muscles of the thigh that is also known as "goose foot".
When asked if Maynard would be back for finals, McRae said: "Well, we're hoping so.
"That's the plan - three to four weeks post procedure that it'll be right. If he doesn't have this procedure, he's probably going to be three or four weeks as well.
"So we're going down the route of managing the things we can control.
"I'll let the medical team announce it. It's quite unique. It's sort of like crossing between a hamstring and a knee injury. There's not too many of them."
Dynamic midfielder Jordan De Goey didn't train on Tuesday.
"He's actually sick. He's got a bit of a viral thing," McRae said.
"He'll be named and we anticipate he plays."
Josh Daicos has pulled up well after pushing through an ankle issue to play in last week's win over Adelaide.
Forward Lachie Schultz (ankle) could play, but will be assessed and have to prove his fitness.
Ruckman Darcy Cameron had a light session after a heavy recent load.
Eighth-placed Collingwood (11-1-7) head into the clash with the ninth-placed Cats (11-8) at the MCG on a six-game winning streak.
Superstar Nick Daicos will have gun tagger Oisin Mullin for company.
"It's hard to think that we'd do anything else," Cats coach Chris Scott said on Tuesday morning.
"... Oisin's obviously been critical to us. But I think I'm on record as saying Daicos is the best player in the comp."
The Magpies are adamant Daicos, whom McRae said had taken his game to another level, can handle the heat.
"I've got a meeting with Nick this afternoon. We meet up regularly and talk about what's coming and what we can do," McRae said.
"The great thing with Nick and what we've done over a number of years now is he's not a target to stand still. And if you're a target that stands still, then you can take things away.
"It's hard to take everything away from Nick because he can play everywhere. So we'll work our way through what that looks like.
"He's (Mullin) done a great job on a couple of really good players in the competition and then he's got our version as well this week.
"We're going to have to be on our game and Nick's critical to what we're doing. So we make sure we get the best of what we can and he might be restricted, but how much - we'll wait and see."