Rob Kearney has been ruled out of Saturday's RBS 6 Nations clash with Scotland, paving the way for Simon Zebo to continue at full-back.
Kearney missed Saturday's 58-15 win over Italy with hamstring trouble, and after further assessment on Monday Ireland have been forced to admit defeat in the British and Irish Lion's fitness bid.
Uncapped Munster flyer Andrew Conway has joined Ireland's squad as cover ahead of Saturday's final Six Nations game at Dublin's Aviva Stadium.
Zebo deputised for Kearney in Saturday's nine-try thumping of Italy and is now in line for the 15 shirt again as Ireland chase victory over Scotland to line up a third-place finish.
"Rob Kearney's hamstring hasn't recovered sufficiently and he will not be involved in Ireland camp this week," the Irish Rugby Football Union (IRFU) confirmed in a statement.
Head coach Joe Schmidt had hoped to have Kearney fit again for Scotland's visit to Dublin, as Ireland seek to ease a disappointing campaign with a second victory this weekend.
Schmidt had anticipated Kearney overcoming his injury when quizzed over the 29-year-old's fitness in the wake of the easy victory over Italy.
Ireland are not yet ready to give up on their other two injury concerns however, with Cian Healy still battling a hamstring strain and Eoin Reddan a calf problem.
Ireland entered the Six Nations as defending champions but are now battling to salvage pride and respect after a tough run of injuries and frustrating performances.
Robbie Henshaw, Andrew Trimble and Keith Earls all received stitches to nasty-looking cuts during the Italy win, but all three will continue training unhindered this week.
"Cian Healy and Eoin Reddan will continue their rehab today with the aim of being available to train tomorrow," read Ireland's statement.
"Robbie Henshaw received some stitches above the eye, Andrew Trimble got a couple of stitches on his nose and Keith Earls received some stitches in his lip."