GEELONG has ruled ruckman Hamish McIntosh out of Friday night's semi-final against North Melbourne.

McIntosh has been struggling to overcome knee soreness in the latter stages of the season, and he was well below his best in the qualifying final loss to Hawthorn.

"Hamish is sore and he won't play this week," Cats coach Chris Scott said at Simonds Stadium on Tuesday morning.

"He's got a sore knee. He's had some knee issues previously - this is not related to those.

"This is a separate issue that he's managed the last few weeks. He didn't play in our last home and away game.

"We were hopeful that that would be enough to have him in good shape for the finals series, but he just laboured too badly on that sore (knee) on the weekend, so we've got to do something about.

"We're hopeful that Hamish can go through a rehab plan over the next week, week and a half, to get himself in a position, if we're good enough to win on Friday night, to play the following week."

Josh Walker and Mark Blicavs are now set to carry the ruck load against the Kangaroos, with Dawson Simpson ruled out for the season after undergoing surgery for a back injury.

"We've got some other more left-field options that we're considering as well," Scott said.

As for what those options are, Scott said, "Tom Hawkins has done a little bit (of rucking) in the past.

"Anyone over 193cm is a candidate."

McIntosh is set to be replaced by a tall forward, with Mitch Brown and Shane Kersten in contention. 

Midfielder Allen Christensen, whose back soreness kept him out of the loss to the Hawks, also remains in the mix to play, although the club is still trying to determine how serious his back problem is. 

Jordan Murdoch is far more likely to take on North Melbourne, despite suffering from hamstring soreness against the Hawks.

Then there's Steve Johnson, who continues to be dogged by a foot problem. 

Johnson started in a blaze of glory against the Hawks, gathering nine disposals in the first quarter.

He faded late in the game, but the Cats are adamant that he's very much in contention to play on Friday night.

"He's in better shape than last time I spoke publicly about (his injury), which was post-game," Scott said.

"Our medical staff and Steve himself are happy with the way he's recovered from the game.

"That doesn't guarantee that he's going to play, but it's certainly a good sign."

If Johnson doesn't play, Brad Hartman, Lincoln McCarthy and Jed Bews are among the potential replacements, with Hartman at the head of the queue.