Leinster have been dealt a blow after South African second row Quinn Roux was ruled out for up to 20 weeks.
The 22-year-old dislocated his shoulder during last Friday's 6-0 victory over Glasgow and will miss the remainder of the Heineken Cup pool stages.
It is the latest set-back for Roux, who is still waiting for his first taste of European action having suffered a fractured collarbone at the beginning of the season.
"He was starting to get a little bit of rhythm," said Joe Schmidt.
"He is a very strong man and we were starting to get a little excited about what we thought he could bring to help us out.
"It's really devastating for him. He is really gutted, obviously. Just the way he fell, his shoulder dislocation, he is probably looking at 16 to 20 weeks' rehabilitation."
"It could happen to any player at any time. He's a 22-year-old kid who I think is a very, very good athlete, very strong who unfortunately landed awkwardly."
The injury leaves Leinster with just four specialist second-rows, Tom Denton, Devin Toner, Damien Browne and captain Leo Cullen.
Leinster recruited All Black Brad Thorne to cover injuries last season but Schmidt has ruled out using a medical joker.
"Thorny is already signed for the Highlanders in New Zealand so there is no going there. At the same time we got Damien Browne back on the field and Tom Denton back from injury as well.
"I don't know if you kept an eye on him on Friday but I thought Leo Cullen trucked around pretty well. Spring chicken that he is. There is still a bit of life in those legs."
But Schmidt has more positive news in the backs with Rob Kearney, Brian O'Driscoll, Luke Fitzgerald and Eoin O'Malley all continue their recovery from various injuries.
Kearney and O'Driscoll have a slim chance of being available for the final group stage rounds of the Heineken Cup in January.
But Leinster are hopeful that O'Malley, and even Fitzgerald, could be involved in the crucial back-to-back clashes with Clermont Auvergne in December.
"Brian and Rob, mid-January is their expected return-to-play date. We'll be guided by the surgeons and the specialists as to what sort of state they are in.
"Luke is in great shape. If you see him out there training he is extremely sharp on his feet.
"It is just a matter of waiting for the all clear for him to take full contact again. That might be one, two, three or four weeks away. I don't expect it to be any more than that. He has made really good progress.
"He's ahead of schedule. We got a bit excited that he might be a bit further ahead than that but unfortunately we have to be patient because he is a top-quality member of our environment.
"Eoin O'Malley is a guy who could possibly be involved this weekend (at home to Zebre) or next weekend in Clermont Auvergne."
Leinster are currently second in Pool Five of the Heineken Cup and trail the French club by two points.
They kick-off their December double-header at Stade Marcel Michelin with the clashes decisive as to whether the Irish province will be able to defend their Heineken Cup crown.
