Rory Best looks likely to be ruled out for several weeks after sustaining a broken arm in Ireland's last-gasp 24-22 defeat by New Zealand.
The Ulster and Lions hooker was forced off in the 15th minute of Sunday's game at the Aviva Stadium, shortly after scoring Ireland's second try.
Best underwent surgery on Tuesday morning and he is expected to return to rugby in mid to late January.
His Ulster team-mate Iain Henderson (hamstring) is out for about six weeks.
Henderson had an MRI scan on the injury that he suffered in Ulster's win over Edinburgh on Friday and it confirmed a hamstring tear.
Like Henderson, Best will miss several of Ulster's forthcoming matches, including the two Heineken Cup games against Treviso.
"Hopefully, I can get back in around eight weeks although we have to see the exact extent of the damage," Best said on Monday.
"As soon as it happened, I heard a crunch. My hand was hanging limp - I had no control over it, I knew straight away.
"It was disappointing to have to go off so early in the match, but it is not completely horrendous news and I have a realistic target to go for."
Next up for Ulster is the away Pro12 game against Zebre on Saturday, which is followed by the back-to-back European matches against the Italians Benetton Treviso on 7 December and 14 December.
The Irish province return to league action at home to Zebre on 20 December before the 28 December away match against Leinster.
There is also concern the fracture could endanger Best's prospects of being fit for the start of Six Nations, with Ireland opening their campaign against Scotland on 2 February.
Ulster have several other fitness concerns ahead of next Saturday's clash against Zebre.
Lewis Stevenson has medial ligament damage to his right knee and will be out for up to six weeks.
Number eight Nick Williams was forced to withdraw from the line-up to face Edinburgh with a recurrence of a calf injury and he is expected to be out of action for four to six weeks.
Michael Allen suffered concussion, while Luke Marshall and Darren Cave were both victims of cramp, but should be available for the clash with Zebre.
A decision on the involvement of skipper Johann Muller and Jared Payne will be made later in the week.
Meanwhile scrum-half Ian Porter irritated his AC joint ahead of the Edinburgh game and is expected to be unavailable for two weeks.