Pendlebury was ruled out in the second quarter of Friday night's 63-point loss to Brisbane with what Collingwood described as a "knee bursa".
The 38-year-old will nervously await the result of scans ahead of a knockout clash against either Carlton or the Western Bulldogs.
"My understanding is like we had some precautionary action around his tightness in the back of his knee and which might be hamstring related," McRae said.
"But it's on the minor side and if there's something there, a scan will show that ... we'll see how that plays out."
"I think anyone that goes off and plays 20 per cent of game time in the last round has to - there's something there - but we won't know until there's a scan."
Eighth-placed Collingwood are currently slated to play the Bulldogs (52 points), unless Luke Beveridge's team lose to Melbourne and Carlton (50) stun leaders Fremantle and leapfrog them into ninth.
In that case, the old rivals would face off.
Pendlebury was substituted four-and-a-half minutes into last year's preliminary final loss to Brisbane with calf tightness.
Collingwood would likely err on the side of caution, desperate to avoid a repeat.
"That'll all be weighed up," McRae said.
"He might be right to go but then do we want to take that risk? That'll be the question that our medical team and high performance team will have to ponder all week.
"Again, you can't make decisions til you get the scan and then work from there.
"So it might it might be as simple as like the scan reveals something and then he won't play.
"So we'll know reasonably early if that's the case and then we'll do what we need to do."
The Magpies were conservative with Isaac Quaynor, Brayden Maynard and Patrick Lipinski, who Collingwood expect to return next week.
Collingwood also managed the game time of Nick Daicos and Darcy Cameron in anticipation of the wildcard game, which McRae insisted felt like a final.
"Well I'll tell you one thing - if Carlton beat Freo tomorrow and the Bulldogs lose I think it'll feel like a final," McRae said.
"It'll be a big crowd here - don't you worry about that and we'll absolutely understand what we're in now.
"It's knockout so when you get into match play - we'll get busy on what that looks like to beat whatever opposition's in front of us and it'll feel like a final."
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