GEELONG midfielder Sam Menegola will miss the next month following knee surgery as the Cats monitor a number of key players ahead of Saturday's clash against the Western Bulldogs.

A late withdrawal last week, Menegola was sent for scans which revealed more serious damage to the cartilage in his knee than first expected.

The 27-year-old will undergo "keyhole" surgery which will rule him out until after the Cats' round 13 bye.

“He is going to need surgery on that, all be it not serious and we are hopeful that could turnaround pretty quickly in a matter of weeks. But with our mid-season bye coming up in a few weeks it would be unlikely that he would play AFL before that," said Geelong Coach Chris Scott.

It comes as the Cats prepare to welcome back Joel Selwood from a two-week lay-off, with Gary Rohan (concussion) and Tom Atkins (hip) to be tested closer to the match.

Selwood missed the round seven win over Essendon with "upper leg" soreness before he was removed from the side last week with a calf niggle.  

Also battling a back complaint in recent weeks, Selwood trained with his teammates in Thursday's main session.

"We think he'll play," Scott said before training.

"Joel, we thought would play (last week), then we didn't think he'd play, then we thought he might play, and he pulled out late.

"This is a case, where we're pretty confident he'll play, but I can understand if you're sitting there thinking, well for two weeks you've been uncertain, why are you certain this week?"

Rohan will need to be cleared from concussion sustained in a head clash with North Melbourne's Sam Durdin that resulted in the Roos' defender being suspended for one-match.

He is expected to be named when teams are lodged on Thursday night at 6.25pm AEST.

"He hasn't been ruled out and the signs are pretty good, but things can change dramatically in 48-hour periods," Scott said.

"We think he'll do a little bit today (at training) but we're optimistic he will play."

Atkins failed to train on Thursday, however Scott said he was "optimistic" the first-year forward would be right to face the Dogs.

All Australian defender Tom Stewart has also been cleared of the neck complaint stemming from the 24-point win over the Roos.

However, Lachie Henderson is expected to miss the next handful of matches after re-injuring his plantar fascia that ruled him out of the start to the season.

"He'll miss 2-3 weeks, we think, but long-term, because he's got a small rupture in that plantar fascia, that will be a better outcome for him," Scott said.