Both Madrid and the Blues came out on top of their respective last-eight ties this week, joining Real Madrid and Bayern Munich in progressing to the semi-final.
Courtois, who is currently in his third season on loan in the Spanish capital from Chelsea, is not prevented from facing his parent club in European competition, although a clause in his contract means the La Liga outfit would need to pay their Premier League counterparts extra should he come up against them in any competition.
The exact amount Madrid would have to fork out is not known, although reports suggest it could be in excess of £4million, a number club president Enrique Cerezo says they would be unwilling to meet.
Speaking to Spanish radio Onda Cero, he said: “It is a figure that we cannot pay.”
The four teams still remaining in the European Cup will learn their semi-final fate when the draw is made on Friday.