Croatia captain Domagoj Vida tested positive for coronavirus after playing the first half of international friendly against Turkey on Wednesday night.
The defender started the game, which ended 3-3, playing the first 45 minutes. He received his test result at half-time and it was positive.
A statement said: “Vida will, in accordance with regulations, spend the next few days in self-isolation in Istanbul.”
All players and staff had tested negative on Monday, but further tests on Wednesday morning found Vida to be positive.