Leinster forwards coach Jono Gibbes believes Sean O'Brien will miss most if not all of the Six Nations following shoulder surgery.
The flanker dislocated his shoulder during the second-half of Leinster's 19-6 victory over Ulster at the RDS on Saturday, and with surgery necessary to correct the problem, it's a bleak prognosis for the British and Irish Lion.
"Further prognosis of that is that he (Sean) is going to have to have a surgical repair on the shoulder. The time frame of that has probably moved him outside of six weeks," said Gibbes.
"The time frame to return to play hasn't been set in stone but it is significant enough for surgical intervention which means six to eight weeks minimum.
"It looks like that (he will miss the entire Six Nations), but they are not going to put an absolute line in the sand for him. They are just going to see how it goes."