Reggie Corrigan has been ruled of the rest of the RBS 6 Nations after breaking his wrist during Ireland's 37-13 win over Italy in Rome.
The Leinster captain suffered the injury just before half-time at Stadio Flaminio, and hospital x-rays have confirmed the worst fears of the Ireland management.
He will be sidelined for between six and eight weeks - ruling him out of Ireland's remaining championship matches against France, Wales and England.
It is a desperate stroke of mis-fortune for the 32-year-old, who was recalled after a three-year absence following the retirement of Peter Clohessy and has managed to rekindle his international career.
He won his 20th cap against Italy, and his absence leaves a massive hole for coach Eddie O'Sullivan to fill.
Munster's Marcus Horan, who played the whole of the second half against the Italians, is set to fill in against the French in Dublin on March 8.
With veteran front-rower Paul Wallace still troubled by a shoulder injury, the selectors are likely to dip into the A team where the Ulster duo of Justin Fitzpatrick and the uncapped Simon Best could come into the reckoning.
Ireland are already without hooker Keith Wood with a long-term shoulder problem and went into yesterday's match without three first-choice backs in Girvan Dempsey, Ronan O'Gara and Shane Horgan.
Conor O'Shea will lead his side to matches against Fiji and Australia
30 March 2017, 2:36pm
After a disappointing RBS 6 Nations campaign for the Azzurri - losing all five of their Championship matches and picking up their 12th Wooden Spoon - they will be licking their wounds ahead of their summer tour Down Under.
The 2017 RBS 6 Nations was watched by record numbers of fans
29 March 2017, 12:25pm
After an enthralling RBS 6 Nations Championship of twists, turns, and no small amount of drama on the last day, figures show the RBS 6 Nations is going from strength to strength, year on year, with no sign of slowing down.