Glasgow and Scotland pair Jonny Gray and Stuart Hogg both face up to six months on the sidelines after undergoing surgery.
Hogg saw his British and Irish Lions tour cut short because of a facial injury, suffering a fracture after colliding with team-mate Conor Murray in the victory over Crusaders.
However, Hogg has had the operation on an “underlying shoulder issue”, which means he is expected to be on the sidelines for four to six months.
Lock Gray has been given the same prognosis for his spell out after returning home from Scotland’s summer tour with a wrist injury.
The injuries mean the pair are likely to miss Scotland’s autumn international series.
The Scots are due to host Samoa, New Zealand and Australia in November at BT Murrayfield.
there was more bad news for Warriors as it was confirmed that 26-year-old Australian winger Ratu Tagive would miss six to nine months of action after rupturing his Achilles during pre-season training.