Scrum-half Chris Cusiter has been ruled out of Scotland's November test series after fracturing his thumb.
The British & Irish Lions player needs surgery on the injury, which he sustained while playing for Perpignan, and will be out of action for about six weeks.
Scotland coach Frank Hadden has also lost centre Graeme Morrison and Rory Lawson, another scrum-half, from his training squad ahead of the Bank of Scotland Corporate Autumn Tests against New Zealand, South Africa and Canada.
Glasgow Warriors scrum-half Mark McMillan has been called into the pool for the training camp in Spain and flew out with the rest of the home-based players from Edinburgh Airport this morning.
Morrison, who scored the decisive try in Scotland's historic Test victory in Argentina in June, was deemed unfit to travel by Scotland team doctor James Robson.
Morrison suffered knee ligament damage in Glasgow's Magners League victory over Leinster and will undergo further assessment and treatment from the Warriors medical staff.
Lawson, who acted as understudy to captain Mike Blair on the summer tour of Argentina, suffered a rib cartilage injury playing for Gloucester yesterday and will see a specialist on Tuesday.
McMillan, 25, has never won a full cap but is a former under-21 captain and represented Scotland A during the summer.
There was better news for Hadden after Ospreys agreed to release winger Nikki Walker for the camp.
Walker will join up with the Scotland squad tomorrow provided he comes through unscathed from his club's match against Worcester.
England flanker James Haskell insists he will be pushing as hard as possible to be back from a toe injury in time to make his case for a spot in Eddie Jones' side looking to defend their RBS 6 Nations title next year.