Sam Warburton says Cardiff Blues fly-half Rhys Patchell is "up and about" and being assessed by medical staff after being carried off during the Pro12 defeat by Ulster.
Patchell spent a night in hospital for assessment after the incident.
Ulster forward Nick Williams has been cited for allegedly striking Patchell.
"He was in today (Monday) being seen by the medics and undergoing the normal concussion protocols," said Blues flanker Warburton.
The Wales captain was rested for the match against Ulster, but said he had been in touch with Patchell after seeing the incident.
"I sent him a text saying I was worried sick about him, but he replied straight away," said Warburton.
"He's up and about, which is great to see."
Williams was sin-binned for a careless challenge after his forearm appeared to connect with the number 10's head in the first half.
Patchell was treated for 10 minutes before being taken off the pitch.
Blues coach Dale McIntosh said after the match that the Ulster forward should have received a red card for the offence on Patchell, who has now returned to Wales.
Ulster won the match 36-17 to lie second in the table, two points behind leaders Glasgow.