Australian opener Justin Langer may sit out the remainder of the third and final Test in South Africa after being hit on the head by a Makhaya Ntini bouncer off the first ball of Australia's innings.
Langer, who was batting in his 100th Test match, was hit behind the ear and received an obvious cut that required attention on the field, but it was the resulting concussion that had officials worried.
The opener was taken to a local hospital to have two stitches for the cut, and treatment for a heavy concussion.
"He felt his arms and legs were weak, every time he sat up he felt very dizzy," team physiotherapist Alex Kountouri told ABC Sport.
"He was getting a headache, he didn't feel steady on his feet, and he couldn't put one leg in front of the other."
Kountouri said Langer was awake and coherent after the incident and at the hospital, but conceded there was a chance he would not resume his innings.
"He remembers the incident, he was watching the game on television in the hospital," he said. "We'll have to review him tomorrow morning and speak to the doctors."
"It will depend on his symptoms. If he's feeling the way he was feeling when he left here, he won't be batting."
Australia was 7-246 at stumps in reply to South Africa's first innings total of 303.