Robbie Henshaw is progressing "more slowly than hoped" in his race against time to be fit for Ireland's match against France on Sunday.
The Leinster back trained last Friday as he recovers from a dead leg, but an Ireland squad update today revealed he's continuing his rehab on a slower timescale this week.
Ireland have taken the unusual step of delaying confirmation of their wider squad until Wednesday morning, with the team to be announced on Friday.
Henshaw has not featured since Ireland's 32-20 opening-round defeat to England, where he was deployed at full-back for just the second time in his Test career.
Joe Schmidt had hoped to have the former Connacht star fully fit to host the French, and has now handed the 25-year-old extra time to prove his readiness.
Fly-half Joey Carbery is said to be progressing well through his hamstring rehab and will have his training load managed early this week.
Last week, Schmidt said if Carbery can train on Wednesday and Friday, he'll be considered for the squad to play France.
Back-row Dan Leavy will continue to increase his running volume outside of team training as he bids to make his comeback from a calf injury in the coming weeks.
Andrew Conway has fully recovered from his cramp suffered after the win over Italy, while players in provincial action have reported no issues.
The squad reassembled last night and trained today at Carton House. The squad will be confirmed tomorrow morning .
France, meanwhile, named their team to travel to Dublin this morning.
- Additional reporting PA
