Ulster full-back Ethan McIlroy was taken to hospital after being knocked unconscious during the United Rugby Championship win over Munster.
The player was able to walk off the field after being attended to by medics but Ulster coach Dan McFarland said he had been "unconscious".
Munster's Shane Daly was sin-binned after the incident but McFarland said the tackle "wasn't malicious".
"Ethan's head was low. He got caught with the arm," said the Ulster coach.
"He was unconscious for a period there. That's obviously concerning but our doctor [Michael] Webb has gone to see him [in hospital] at the moment."
McIlroy was tackled just short of the Munster line as he attempted to cancel out the first of Craig Casey's two first-half tries.
Ulster trailed 14-3 early on but tries from Jacob Stockdale and Nick Timoney, in addition to 11 points from Nathan Doak, helped them fight back to beat the United Rugby champions 21-14.