Thibaut Courtois could be denied the opportunity to face his parent club Chelsea in the Champions League semi-final or final because of a prohibitively expensive clause that was inserted into his latest loan agreement at Atlético Madrid.

The Belgium goalkeeper helped his team to a quarter-final victory over Barcelona on Wednesday night and, like everybody connected to Atlético, he will watch Friday's semi-final draw with great excitement. Atlético could meet Chelsea, who advanced after their comeback triumph over Paris Saint-Germain, but that would stand to spell heartbreak for Courtois. The Atlético president, Enrique Cerezo, has confirmed the existence of a clause in Courtois's deal that would require the club to pay "a big quantity of money" if they wanted the player to face Chelsea, from whom the outstanding 21-year-old is on loan for the third consecutive season.

It is understood the figure is €3m per game and, with Atlético's financial situation making them reliant on loans and third-party investment, that may be beyond them, particularly over two legs of a semi-final.

"The problem if we got Chelsea would be whether Courtois can play or not," Cerezo said. "It is possible that he won't be able to play. Is that in the contract? Yes, of course. I imagine that if he plays, it will need a big quantity of money [to be paid]."

Unlike in the Premier League, where loan players cannot face their parent clubs, there are no such restrictions in the Champions League. Courtois played well for Atlético against Chelsea last season, in the Spanish club's Super Cup victory and, if that was slightly embarrassing for Chelsea, it may have motivated them to insert the clause into Courtois's latest deal

Chelsea say that it is up to Atlético to decide whether they may want to select Courtois against them. They made no comment on the specific clause in question.

José Mourinho, meanwhile, is understood to be furious at the £8,000 fine that he has received from the Football Association for his recent sending-off at Aston Villa. The Chelsea manager, who has also been warned about his future conduct, will await the full written reasons for the FA's judgment before giving his response.