Atletico Madrid unlikely to test Chelsea relationship fielding Courtois
UEFA told both clubs their agreement stating Atletico must pay £2.5m per game if Courtois plays against parent club Chelsea goes against their rules.
Atletico previously claimed they couldn't afford the appearance money for their Champions League semifinal.
But they risk ruining their relationship with Chelsea if they try and field Courtois for free following UEFA's intervention and go back on their word over payment.
The Spaniards want to loan Courtois again for a fourth season next year but their hopes will be over if the two clubs fall out.