But Lions head doctor, James Robson, says the 23-year-old has recovered very well and a final check-up with an independent neurologist on Monday should clear the way for him to play against the Emerging Boks.
"James will see the same neurologist as we used to check on Ryan Jones earlier in the tour. If he gets the all clear from him, then he will be available for selection for Tuesday," said Dr Robson.
"We are following the normal IRB protocol after a player has suffered concussion. We closely monitored his symptoms after the injury, eased him back into some form of exercise and, for the past two days, he has returned to non-contact rugby training.
"James feels well and I would expect the neurologist to pass him fit to play."