Tadhg Beirne will undergo an ankle operation today and will be out of action for up to 12 weeks.
The development is bad news for Ireland, as the versatile second row and back row will miss the remainder of the Six Nations, and also for his province Munster.
The time frame for Beirne's return is early May and that means the Kildare man is out of Munster's Champions Cup last 16 clash away to the Cell C Sharks, and out of a potential quarter-final and semi-final appearance if the province goes that far in the tournament.
The 31-year-old suffered the injury early in the second half of Ireland's 32-19 victory over France in the Six Nations last Saturday.
Immediately afterwards, Ireland boss Andy Farrell described the expected prognosis as "not good" and Beirne left the stadium in a moonboot and on crutches.
It is a blow for Farrell as Beirne has developed a strong second row partnership with James Ryan, but he will now call on the experienced Ulster skipper Iain Henderson to step up.
And the player is added to a casualty list that had already left the Ireland boss without four regular starters for the France game - Dan Sheehan, Tadhg Furlong, Jamison Gibson-Park and Robbie Henshaw.
Farrell hopes that up to two of that quartet will be able to return for Saturday week's third round clash with Italy in Rome - certainly the indications are that Sheehan will be available again after his hamstring problem.
"Tadhg’s headed in for an operation today," confirmed Ireland defence coach Simon Easterby.
"The high ankle issue means he's going to be between 10 and 12 weeks out of action.
"It’s quite a common operation these days, a procedure which other players have had to go through and hopefully the operation goes well and he’s back up and running and ready to go in about 10 to 12 weeks."
Easterby acknowledged that losing Beirne is a blow to the Ireland set-up with three games remaining in the championship, but he insisted the cover was there to compensate.
"Tadhg has been phenomenal, hasn’t he, over the last couple of seasons," he said.
"But like we’ve already had to do over the course of this championship we lost players before the game against Wales.
"We’ve had to adapt and that’s testament to the squad and the players within, even those guys who might not expect to be involved, they come in and the standard of performance doesn’t drop.
"It’s really unfortunate that we’ve lost Tadhg but we’ve very fortunate with the stocks that we have available to us in his position and other players have done that, they’ve stepped in and the performance hasn’t dipped.
"It’s part and parcel of the game. World Cup, you could be without a player for a few weeks and we might keep over a player and someone else has got to step in and having the ability to deepen our experience in the squad.
"And playing in big games is part and parcel of us being the best we can be, whether it’s the best 33 in the World Cup or if we have to dig deeper to 45 players and that’s the mentality that was there a couple of years ago, to make sure that we have more than just 30, 31, 32, 33 players available.
"Certainly we have drilled down into players underneath those and we feel like we are in a much better place to lose someone like Tadhg and not lose performance in players that come in. "
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