Scotland lock Richie Gray suffered concussion in Saturday's 21-10 loss to South Africa at Murrayfield.
The Sale Sharks second row, who was winning his 26th cap, was injured during the first half when he took a knee to the head and is a doubt for the final match of the Scotland's November Test series against Tonga in Aberdeen next Saturday.
"Richie will now be subject to the return to play protocol following a concussive episode," said Scotland doctor James Robson .
"We have been in contact with his club medical team at Sale Sharks to discuss the management of his injury."
The only other injury doubt is flanker Alasdair Strokosch, who was a late withdrawal from the team on Friday.
"Alasdair Strokosch is continuing his rehabilitation with us following the calf strain he sustained in training last week," said Robson.