Ultan Dillane has been ruled out for the rest of the season after going under the knife to rectify a shoulder problem.
The Connacht lock missed the Six Nations, requiring surgery on an injury that ruled him out of Joe Schmidt's plans.
He'll now spend the next two months recovering and will play no part in the climax to the Pro12 campaign.
Pat Lam's men head to Glasgow Warriors this Saturday without Nepia Fox-Matamua, who sustained an ACL injury in the game against Treviso and will undergo surgery himself next week.
Peter Robb suffered a hip injury in a club game and could be out for a month.
Conor Carey is continuing his recovery from his foot injury and should be back by mid to late April, while Matt Healy injured his hand in training last week.
Marnitz Boshoff has returned to South Africa following the sudden passing of his father.
On a more positive note, Josh Rowland is back in full training with the squad.
Ireland squad members Kieran Marmion, Tiernan O’Halloran and Quinn Roux have all returned to the province and are also available for selection.
