Ireland will give CJ Stander, Rob Kearney and Simon Zebo every chance to prove their fitness for Saturday's Test clash with Australia.
Flanker Stander and fullback 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.
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"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.
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 to Ireland.
"Keith has managed to train today, Ultan was carrying a bump from his performance against Canada so those guys are back on board," Easterby said.
"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."
