Tommy Bowe is a major doubt for the Six Nations after suffering ligament damage playing for their Ulster in the Heineken Cup at the weekend.
Leinster hooker Richard Strauss suffered a medial ligament injury as Leinster lost at home to Clermont Auvergne and is expected to be out for four weeks.
Bowe suffered a significant knee injury playing for Ulster in their defeat to Northampton.
Meanwhile, Ireland captain Brian O'Driscoll trained with Leinster today after recovering from ankle surgery.
Winger Bowe is now considered a doubt for the 2013 Six Nations championships, and possibly the British and Irish Lions tour to Australia, after suffering a significant knee injury playing for Ulster.
The 28-year-old, who can also play in the centre, suffered the injury at the end of the Irish province's 10-9 loss at home to the Saints, their first defeat of the season.
"He has sustained significant lateral ligament damage to his right knee," a statement on the Ulster website said.
"He will undergo surgery later this week to repair the damage. At this stage it is not possible to put a timescale on how long his recovery period will be."
Ireland begin their Six Nations campaign in Cardiff against Wales on 2 February, with the first Lions tour match against the Barbarians in Hong Kong on 1 June.
Bowe was an impressive performer on the last Lions tour in South Africa in 2009, starting all three tests, and has scored 26 tries for Ireland in 51 matches.