Iain Henderson is expected to miss the majority of Ireland's Six Nations campaign after undergoing surgery to repair a torn thumb ligament.
British and Irish Lion Henderson is set for 10 weeks on the sidelines, ruling him out of defending Six Nations champions Ireland's clashes with England, Scotland and Italy.
If the Ulster lock's recovery goes as planned, he could be in contention to face France in Dublin on March 10.
Henderson scored two tries as Ulster defeated the Scarlets 30-15 in the European Champions Cup on Friday, though they remain five points adrift of unbeaten Pool 4 leaders Racing 92.
The 26-year-old will miss their final two group games against Racing and Leicester Tigers.
