Winger Darcy Graham will miss Scotland's Six Nations opener against Ireland next Saturday due to a knee injury.
And the Edinburgh back could also miss the match with England, with Scottish Rugby saying ligament damage will keep him out of the "opening rounds".
Meanwhile, Worcester Warriors fly-half Duncan Weir has been added to the squad in place of Finn Russell.
Russell was disciplined for a "breach of team protocol".
The incident related to alcohol consumption and a missed training session, so the 27-year-old Racing 92 fly-half told he would not be considered for the trip to Dublin.
Weir earned the most recent of his 27 caps in the 2017 Six Nations and will now join the squad as they prepare to fly out to Spain for a training camp.
He is the only addition to the 34-man group, with Edinburgh prop Jamie Bhatti, Glasgow Warriors back-row Tom Gordon and Sale Sharks wing Byron McGuigan joining Russell as players from the wider squad not to travel.