Conor Murray has not linked up with the Ireland squad ahead of Saturday's autumn Test with Argentina in Dublin.
The scrum-half will instead return to Munster to continue his rehabilitation from a long-standing neck injury.
Ireland assistant coach Greg Feek did not rule Murray out of facing world champions New Zealand on 17 November but he seems unlikely to feature.
Murray, 29, has not played since Ireland beat Australia in the decisive third Test of their tour in June.
The British and Irish Lion was not named in Ireland coach Joe Schmidt's original 42-man squad for the autumn internationals but last week forwards coach Simon Easterby indicated that the number nine had not been ruled out of facing the All Blacks at the Aviva Stadium.
Murray did join Ireland for three days' training last week, during which he stepped up his recovery under the supervision of the IRFU medical team.
Asked about Murray, Feek said: "Yeah, he's not in camp. Again it's another one that we're just monitoring and I'm still getting up to speed with all that as well.
"It's something that obviously not being here this week, they're freshening him up and it is just trying to tick some boxes to get back in the frame.
"We already have three half-backs there so there's no point in carrying one more."
Murray's absence from Ireland's Carton House training base this week means the accomplished half-back will certainly miss the clash with the Argentines.
Luke McGrath, who started last Saturday's 54-7 demolition of Italy in Chicago, John Cooney and Kieran Marmion are all in the mix to play, with McGrath the most likely to get the nod.
Kearney fitness battle
Leinster full-back Rob Kearney continues to battle for fitness, with Feek rating the 32-year-old's chances of facing the Pumas at "50 per cent".
Jordan Larmour is waiting in the wings to deputise in the number 15 shirt if Kearney fails to recover fully from his shoulder problem.
"He's probably in the middle 50 per cent," said Feek of Kearney.
"Rob was working with the physios today. We will see how he goes but it is just a case of getting there.
"We will wait and see how he comes through. He was doing stuff with the medics and is on his return (to play).
"Hopefully things will progress for him. Firstly Rob Kearney is Rob Kearney, he's a good man to have in the team, offers a lot of experience.
"In saying that we have good depth in the squad. This series is all about that, testing our depth in the squad, making sure that people can slot in and things can carry on."
Regular front-line players such as Jonathan Sexton, Tadhg Furlong and James Ryan are expected to return when the team is named on Thursday.