David Denton, the 24-year-old Edinburgh Rugby back-row forward, will play no part in Scotland's summer tour.
Denton was due to challenge for a place in this Friday's Test against Argentina in Cordoba and for the closing match against South Africa in Port Elizabeth a week on Saturday.
Now however injury has ruled him out.
Scotland team doctor James Robson explained: "David suffered a concussion in his last game of the season for Edinburgh against Leinster in the PRO12 last month.
"As we've always said we regard the welfare of our players as our principal priority and David has not recovered sufficiently to be considered for the intensity of Test match rugby against Argentina and South Africa.”
The Scotland management will now consider additional options for the South African leg of the tour, while remaining mindful of the preparations that are already underway for the 2014 Commonwealth Games 7s in Glasgow next month.
Current Scotland squad in Argentina: Backs: Stuart Hogg, Peter Murchie, Sean Maitland, Tommy Seymour, Dougie Fife, Nick De Luca, Peter Horne, Tom Heathcote, Duncan Weir, Henry Pyrgos and Grayson Hart. Forwards: Gordon Reid, Alasdair Dickinson, Kevin Bryce, Pat MacArthur, Ross Ford, Jon Welsh, Geoff Cross, Moray Low, Tim Swinson, Grant Gilchrist, Jonny Gray, Kieran Low, Robert Harley, Blair Cowan and Chris Fusaro.