Champions League draw: Chelsea weigh up pros and cons of allowing goalkeeper Thibaut Courtois on loan at Atletico Madrid to play

Chelsea are facing a damaging row with Atletico Madrid about whether to allow their on-loan goalkeeper, Thibaut Courtois, to play against them if the two clubs are thrown together in Friday’s Champions League draw for the semi-finals and final.

It will be one of the proudest moments in Atletico Madrid’s recent history and the highlight of Courtois’ career but it could also spell the end of his participation in a competition he has dominated.

No keeper has let in fewer goals in this season’s tournament with the Belgian conceding only five. But a clause in his loan contract will prevent him playing against Chelsea unless the Spanish club are prepared to pay a huge fee to the Londoners, believed to be around £4.5m, for the two matches. A fee would also be due if the two sides were to meet in the final instead. Last night, Chelsea would not comment on the contractual situation.

“If I had the money I would pay for him to play myself,” said midfielder Koke, who scored Atletico’s winning goal against Barcelona this week. The club’s president, Enrique Cerezo, had earlier admitted that it was a “large sum of money” which the club “could not afford”.

Courtois has delayed signing a new contract at Chelsea because he is unhappy at being owned by one club and playing for another. Unlike in the Premier League, clubs in Uefa competitions cannot ban players they loan out from lining up against them, unless the contracts between the clubs include clauses that mean the borrowing club must pay for the player to be eligible.

Chelsea inserted such a clause in Courtois’ latest loan deal at the start of the season after suffering at his hands in the European Super Cup in 2012. He hopes that Chelsea can be convinced to drop the fee as part of the final stages of the talks over a new deal.

The two parties are close to agreeing a five-year extension but are still in discussions over salary. Atletico are also considering the prospect of selling striker Diego Costa, who has a £32m clause in his contract, for a reduced fee to Chelsea this summer in exchange for Courtois playing for free.

It will be the first time in seven years that Barcelona have not been in the last four and with their transfer ban looming their immediate future in a competition they have won three times in the last 11 years looks bleak.

Lionel Messi and manager Gerardo Martino bore the brunt of the criticism for their defeat by Atletico. Statistics revealed Messi had run only twice the distance of his own goalkeeper Jose Pinto.

Martino was undone by his own words. “We weren’t really interested in Messi having a lot of participation in the game. We just wanted him to have one-on-one situations down the right,” he said.