The Irish Rugby Football Union (IRFU) has confirmed Josh van der Flier will be sidelined for the rest of the 2017-18 season after suffering a serious knee ligament injury in his country's Six Nations victory over France.
Van der Flier was hurt late in the first half of Saturday's match at the Stade de France, with Ireland coach Joe Schmidt subsequently stating he feared a long-term lay-off was likely for the flanker.
On Monday, an IRFU statement confirmed the 24-year-old had been ruled out for the remainder of the campaign.
The news comes as a blow to Ireland and Van der Flier's club Leinster, who are bidding for glory on two fronts domestically in the Pro14 and European Champions Cup.
Leinster face a Champions Cup quarter-final with reigning champions Saracens on April 1, but will now have to make do without one of their star performers.
Ireland snatched victory in Paris courtesy of a last-gasp drop goal from Jonathan Sexton and will be expected to make it two wins out of two in the Six Nations when they welcome Italy to Dublin on Saturday.