Ospreys captain Alun Wyn Jones has been ruled out for up to 16 weeks after injuring his shoulder playing for Wales.
Jones damaged AC joint ligaments in his country's 26-12 defeat to Argentina in Cardiff on Saturday and he must now undergo surgery to rectify the problem.
The lock misses Wales' upcoming autumn internationals with Samoa, New Zealand and Australia and could also miss the start of the Six Nations.
He will also sit out the remainder of Ospreys' Heineken Cup Pool Two campaign.
"After carefully reviewing the scans and discussing the best management of the injury with specialists, the recommendation was made for Alun Wyn to undergo surgery in order to give him the best chance of making a full recovery," read a statement on the Ospreys' official website.
"He is due to undergo the surgery at the end of this week, and we will be looking at a 12-16 week rehab process post-op to get him back on the field," said Ospreys Head Physio Chris Towers.