Mateo Musacchio was stretchered off during AC Milans clash with Real Betis after being knocked out cold by his team-mate Franck Kessie.
The Europa League group game ended 1-1, but was overshadowed by the worrying injury to the Milan defender, who was in a neck brace when he left the pitch.
Kessie collided with his team-mate as both players went for the same ball in the closing stages of the match, and Musacchio immediately went limp.
Players called for medics and Musacchio was turned on his side as he regained consciousness, before he was driven off the pitch on a stretcher.
Sky Italy reported after the game Musacchio was conscious in the dressing room and told reporters as he left the stadium he was fine.
There is optimism at Milan that the injury is not as serious as first feared.
The 28-year-old is a key player for Gennaro Gattusos side having played every minute of Serie A football this season.
Milan are back in action on Sunday in a huge game against Juventus, but Musacchio is unlikely to available if he did suffer concussion.
Watch the collision below…