Sergio Aguero was taken to hospital following his early substitution against Deportivo Alaves, Barcelona have confirmed.
The Argentina international was making his first LaLiga start at Camp Nou, but was replaced by Philippe Coutinho after just 41 minutes.
Aguero went down clutching his chest and was tended to by the medical team, although he was able to get to his feet and walk from the field.
The club later confirmed the former Manchester City striker had complained of chest discomfort and had been admitted to hospital for a cardiac exam.
Barca also lost Gerard Pique to a right calf strain during the 1-1 draw.
"[Aguero] told me he was a little dizzy," interim coach Sergi Barjuan told Marca.
"Now, I have learned that he has been taken to the hospital. I can't say more.
"Between cheering on the guys and the press conference, it's hard to know more."
Sergi's first match as coach
The stalemate marked Sergi's first match in temporary charge following the departure of Ronald Koeman earlier this week.
Memphis Depay's sublime strike was immediately cancelled out by Luis Rioja and despite just under 80 per cent of possession and 16 shots on goal, the hosts were forced to settle for a share of the spoils.
"We controlled the game, and we were intense in the second half," Sergi continued.
"We had our chances to score and win the game, but we could not take them.
"I have had very little time to work with the players. I have tried to get them in order in both a defensive and an offensive level.
"But, these players are very good, and they have to believe in themselves."