Leinster lock Quinn Roux is facing up to five months on the sidelines after dislocating his shoulder in last weekend's win over Glasgow.
The South African, who joined the Heineken Cup winners from Western Province last summer, had impressed for the province after recovering from a broken collarbone.
Roux was forced to leave the pitch during the first half of Leinster's 6-0 win at Glasgow in the RaboDirect PRO12, and coach Joe Schmidt confirmed he faces '16 to 20 weeks' of rehabilitation.
"I don't know if you saw it but he was starting to get a little bit of rhythm," said 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. Just the way he fell, his shoulder dislocation, he is probably looking at 16 to 20 weeks' rehabilitation."
Leinster signed Roux after fellow South African Steven Sykes failed to impress and Brad Thorn's short-term deal expired at the end of last season.
There was some positive new for Schmidt however, with Brian O'Driscoll and Rob Kearney set to return for their final two Heineken Cup games in January and Luke Fitzgerald waiting for the all clear to take full contact training.
"Luke's ahead of schedule," said Schmidt. "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."
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