Leinster flanker Josh van der Flier is "likely to miss the rest of the season" with a groin injury.
The Ireland international injured his leg against France in the Six Nations and Leinster today revealed he underwent surgery and will be out for 12 weeks.
Head coach Leo Cullen was not hopeful on the wing forward's chances of reappearing this season.
"He’s back in there [Leinster camp] today, the surgery has gone well for him but again he’s likely to miss the rest of the season unless there is some magic cure between now and then," Cullen said.
"Josh has been incredibly unlucky and he had been going incredibly well for us this year. He works hard, just another blow for him but hopefully he’ll be able to get himself in good shape again to get ready for World Cup plans."
The European champions take on Ulster this weekend in the Heineken Champions Cup quarter-final and Cullen added that Robbie Henshaw, whose last appearance came at the start of February for Ireland against England, is back training but rated as "less likely than likely" to make the panel on Saturday.
Cullen said that the centre saw a specialist in the UK to address why the dead leg was taking so long to heal.
The coach said: "Whatever way the tear in the muscle was... the dead leg was initially what the cause of concern was but there was a little bit more damage a bit deeper in.
"So it was a little bit unusual, probably, from initially the way it presented, obviously as a dead leg.
"He had a little minor procedure done but I couldn't get into the technicalities of that."
Out-half Ross Byrne, who was a late withdrawal before Leinster's Pro14 defeat to Edinburgh at the weekend, will "be further assessed this week", while Noel Reid and Sean Cronin are undergoing graduated return to play protocols after suffering head injuries in Murrayfield.
Returning players Joe Tomane, Luke McGrath, Dan Leavy and Nick McCarthy all came through with no injury issues and are available for selection this week.