Rob Kearney will start at full-back for Ireland's RBS 6 Nations clash with Wales after Geordan Murphy and Girvan Dempsey failed fitness tests on Thursday.
Ireland coach Eddie O'Sullivan was prepared to give rivals Murphy and Dempsey until lunchtime to prove their availability for Saturday's Croke Park showdown.
But their failure to recover in time has forced O'Sullivan to implement his contingency plan with Kearney of Leinster moving from left wing to full-back.
Ulster's Tommy Bowe switches flanks to take Kearney's place on the left, Shane Horgan is promoted from the bench to plug the gap at 14 and Luke Fitzgerald is called onto the bench.
An Irish Rugby Football Union statement read: “Following a fitness test before the Ireland training session today, both Geordan Murphy and Girvan Dempsey have been ruled out of the Six Nations game against Wales due to Achilles and hip injuries respectively.”
Dempsey withdrew from the team that demolished Scotland 34-13 because of his hip injury and Murphy, his replacement, went on to produce a man-of-the-match display.
Murphy was then struck by an Achilles tendon problem while on club duty for Leicester last weekend and was added to Ireland's casualty list.
His star turn against the Scots had left O'Sullivan with possibly the toughest selection dilemma of his Ireland tenure as the ever-dependable Dempsey had been his most reliable performer over the last 12 months.
The rivals' fitness battle allowed O'Sullivan - who would have been heavily criticised whatever his decision - to let the healing process make the call.
But when neither player was given the green light, a reshuffle involving the return of veteran Leinster winger Shane Horgan for his first Ireland start since the World Cup became necessary.
The developments will give O'Sullivan the chance to run the rule over Kearney, whose long-term future appears to be at full-back.
Kearney, a solid defender with a big boot, has acquitted himself well so far during the Six Nations.
The 21-year-old will be winning only his fifth cap on Saturday but he has adjusted swiftly to the demands of Test rugby and offers a cutting edge from deep.
It is an unfortunate turn of events for Bowe, who must redeploy to the left after plundering two tries against Scotland from his preferred right wing position.