Andrew Henderson, the 27-year-old centre, will miss Scotland's opening Rugby World Cup match against Portugal in St Etienne on Sunday.
Henderson has what the Scotland medical team have described as a "nasty" dead leg, sustained in last month's match against South Africa.
Head coach Frank Hadden confirmed: "Andy is undergoing intensive treatment from our medical team but the injury will preclude him from selection for Sunday's game."
Henderson did some light running and passing drills with Scotland team masseur Dougie Mills when the squad trained at L'Etrat, their base camp, this afternoon.
All other 29 players in the squad participated in full in a training session watched by around 100 local people, including a class from the nearby primary school.
Tonight at a formal ceremony in the St Etienne town hall the Scotland squad will be presented with their Rugby World Cup caps.
Earlier in the day Hadden, captain Jason White, assistant coach George Graham, manager Guy Richardson and a host of senior players were at the same venue for an official introductory media conference.
All were at pains to stress how favourable an early impression the town, its people and training facilities had made on the party.
Hadden was asked what he expected from the Portuguese team on Sunday. "It will be tough," he reasoned. "They've improved their performances over the past year and I noticed on Tuesday that L'Equipe (the French sports newspaper) had listed their outside centre in their world XV.
"However our focus will be on our performance. We've been in the planning and preparation phase for some time now for what is the biggest sporting event in the world this year.
"Arriving in France yesterday brought home to us the significance of the World Cup and we just can't wait to get started."