Cian Healy could miss the start of Ireland's Six Nations campaign after undergoing surgery on an ankle injury.
The Leinster loosehead prop has been ruled out for eight weeks, leaving him in a race against time to be fit to face Scotland on 2 February.
He sat out last weekend's Heineken Cup win at Northampton and was already out of the return in Dublin on Saturday.
"It was syndesmosis and they repaired that," Leinster coach Matt O'Connor said. "He won't play for a while."
Confirming the longer spell on the sidelines on Thursday, O'Connor added that Healy is "doing good" after surgery on Wednesday.
Healy had surgery on his left ankle during the summer to correct an injury sustained on the British and Irish Lions tour to Australia and has made just four appearances for Leinster this season.
The highly-rated Jack McGrath is likely to start at loosehead against Northampton Saints on Saturday, while Michael Bent, whose preferred position is tighthead, will provide cover on the bench.
Sean O'Brien remains a concern for this weekend, meanwhile, after picking up a dead leg against the Saints last week.
"Sean trained alright so we'll wait and see. We'll give him as long as possible and hopefully he'll be right (for Saturday)," added O'Connor.