Ireland will be without Ulster duo Iain Henderson and Tommy Bowe for the Six Nations.
Both were doubts for the tournament with Henderson out since December with a hamstring injury and Bowe sidelined by the knee ligament injury he suffered in the Rugby World Cup quarter-finals.
Henderson, who has 23 caps, is facing a race against time to play any further part this campaign and is a doubt for Ireland's tour of South Africa in June. "It looks like Iain will be out for the remainder of the season," Ulster coach Neil Doak told journalists this week. "It's unfortunate, but that's the way it is."
The news is better on Bowe with the British & Irish Lions winger hopeful of playing again this term. "Unfortunately it's a slow process and to rule yourself out of the Six Nations is disappointing," Bowe told the BBC. "I have to concentrate on getting myself back to where I was and there's no point in rushing it.
"To be back by the start of February is unlikely but I'm still pretty positive I can add something to Ulster's season."