Leinster have confirmed that inspirational flanker Sean O'Brien will need surgery on the dislocated shoulder he sustained against Ulster on Saturday, ruling him out of Ireland's opening Six Nations games.
Forwards coach Jono Gibbes said he expected the Carlow man to be out for "six to eight weeks minimum", meaning he would definitely miss the games against Scotland, Wales and England.
If that time frame proves accurate, O'Brien might be fit to return for the final fixtures - against Italy at Landsdowne Road on 8 March and France in Paris on 15 March - but he could struggle to play any part in the tournament.
The news is a huge blow to Ireland coach Joe Schmidt ahead of his first Six Nations in charge and to Leinster, who face crunch Heineken Cup clashes with Castres and Ospreys this month.
