Irish management have confirmed Rob Kearney's hamstring has not recovered sufficiently and he will not be involved in Ireland camp this week ahead of the game against Scotland.
The Leinster full-back missed Ireland's win over Italy on Saturday with the same injury, with Simon Zebo filling in at 15.
Ulster's Jared Payne, who started at outside centre against the Italians, is another option for the 15 shirt.
Uncapped Munster back Andrew Conway has joined the squad as cover.
Loosehead prop Cian Healy and scrum-half Eoin Reddan remain doubts for the Scotland game but will continue their rehab today with the aim of being available to train tomorrow.
Meanwhile, Scotland have injury problems of their own to contend with after yesterday's win over France.
Out-half Finn Russell sustained a concussion early in the match and is now subject to the return-to-play protocols.
Second-row Jonny Gray will have a scan today on a pectoral strain while several other players are nursing cuts and bruises from the win at Murrayfield.
A win over Scotland could lift Ireland as high as second in the Six Nations table depending on other results - Wales would have to lose to Italy which is unlikely - on the final day, while defeat would see Joe Schmidt's side finish fifth.
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