Atletico Madrid president Enrique Cerezo has admitted that goalkeeper Thibaut Courtois would probably not be able to play against Chelsea if the clubs are drawn together in the Champions League semi-finals.
The Belgian goalkeeper helped Atletico beat Barcelona 1-0 at the Vicente Calderon on Wednesday in the second leg of their quarter-final to take them through to the semi-finals 2-1 on aggregate.
The Spanish capital club will join their city rivals Real, defending champions Bayern Munich and Chelsea in Friday's semi-final draw, but they will hope to avoid being paired with the latter.
"Courtois is a Chelsea player. We are trying to reach an agreement for him to stay with us for another year," Cerezo told radio station Onda Cero when asked about Courtois, who is on loan from the London club.
"The problem is that if we play against Chelsea he might not play."
When asked if that was written in the loan agreement, Cerezo replied: "Yes, of course. If he plays we will have to pay a lot of money."
Madrid-based sports daily AS have suggested that Atleti would have to pay 3 million euros (Â£2.48m, $4.17m) for each game Courtois plays against Chelsea, meaning the figure would be doubled if he were to feature in a two-legged semi-final.
Cerezo added that his dream is to meet Bayern in the final. In Atletico's only appearance in the final of the European Cup, in 1974, they were denied victory against Bayern in Brussels when Georg Schwarzenbeck scored an equaliser to make it 1-1 in the last minute of extra time.
Bayern went on to win 4-0 in a replay two days later at the same venue.