Barcelona defender Gerard Pique was taken to hospital after colliding with goalkeeper Victor Valdes during the Champions League semi-final exit to Chelsea.
Pique, restored to the starting line-up, collided with his team-mate 17 minutes into the game and appeared to briefly lose consciousness.
He attempted to play on but looked to be dazed in the aftermath and, nine minutes after the incident, he was replaced by Dani Alves.
"Pique felt dizzy," Barca sporting director Andoni Zubizarreta said. "He has been taken to hospital to undergo more tests."
Barcelona subsequently announced that Pique had suffered no damage but would be kept in hospital overnight.
Chelsea secured a 2-2 draw in the game to win the tie 3-2 on aggregate and reach the final at the Allianz Arena.