Glasgow and Scotland have been hit with a triple injury blow after internationals Fraser Brown, George Horne and Alex Allan were ruled out for lengthy periods.
Warriors have ruled co-captain Fraser Brown out for at least three months following further examination of the neck injury he suffered while playing for Scotland in their Autumn Nations Cup match against Ireland.
Scrum-half Horne has been told he needs surgery on a foot injury which he developed while training with Scotland during the autumn.
Both will miss the entire Six Nations campaign.
Allan has had successful surgery on the Achilles injury he sustained while playing against Dragons in early December. The prop is expected to be unavailable for the remainder of the season.
Scotland begin their Six Nations campaign with a trip to Twickenham to face defending champions England on February 6.