Flanker Stander and full-back Kearney are working through head injury checks after concussions, while Zebo continues to suffer the after-effects of cramping during Saturday’s gruelling 21-9 defeat to New Zealand.
Ireland are loath to lose any more frontline stars to face the Wallabies at Dublin’s Aviva Stadium, with Johnny Sexton and Robbie Henshaw already ruled out.
So head coach Joe Schmdit could take the rare step of allowing a nucleus of stars to return to full training on Thursday – before settling on his final line-up for Australia.
“They are on track, they are following the return to play protocols and are covering off those (markers) as we would expect,” said Ireland assistant Simon Easterby of Stander and Rob Kearney.
“We will know later in the week as they go through those protocols.
“Simon (Zebo) has managed training today and got through some work.
“He, like some other players in the group, are being managed, to get them right for Thursday, when we can select the team based on who is available.”
Stander and Kearney must pass all the relevant stages of the rigorous head injury tests before being cleared by Ireland’s medical team to return to full training.
Ireland boss Schmidt would in an ideal world start his Test-match selection process in earnest after training on a Tuesday building up to a Saturday match.
The former Leinster coach has delayed his selection to cover the Thursday training run in the past however, and now looks likely to do the same again.
Fly-half Sexton will miss Ireland’s final autumn clash against Australia in Dublin with a hamstring strain, while Henshaw has already been ruled out through concussion.
Utility back Keith Earls trained fully on Tuesday after missing the All Blacks defeat through a dead leg, while lock Ultan Dillane has beaten a minor knee issue.
Munster star Earls’ recovery offers a significant midfield boost, with Sexton and centre Henshaw already missing and Zebo and Kearney still doubtful.
Earls’ ability to feature at full-back, centre and wing could almost now guarantee him a start against the Wallabies amid Ireland’s fluid selection process.
“Keith has managed to train today, Ultan was carrying a bump from his performance against Canada so those guys are back on board,” said Easterby.
“They will have been disappointed to miss out on the opportunity to play last weekend but it is obviously good to have some guys coming in who are a little bit fresher and ready to put their hands up for selection.
“First and foremost we want to try and get a performance (on Saturday) and keep building some consistency.
“Yes we want to build depth; that probably goes back to the World Cup time when we didn’t quite have that depth in certain positions.
“But it is important to get the balance right. We have lost a few players already after the weekend, we want to keep some consistency (in selection) but we always want to build some depth going into the Six Nations and this weekend might allow us to do that.
“The players put themselves through a hell of a workload at the weekend.
“It’s important we get them right in the first part of the week, so we can build up in to Thursday and Friday and get them in a really good physical and mental state for Saturday.”