A compromise on Diego Costa's €60m release clause will be considered by Atletico Madrid if Chelsea allow Thibaut Courtois to play against them in the Champions League, reports El Confidencial.
Belgian international Courtois hit the headlines the moment Atletico and Chelsea were drawn together in the semi-final of Europe's elite competition.
Although there is nothing in Uefa regulations to prevent Courtois from playing against his parent club Chelsea, it is believed Atletico will have to fork over as much as £5m to allow their loan star to play in both legs.
Courtois will be key to Atletico's chances of beating former winners Chelsea as their back-up goalkeeper Daniel Aranzubia has only featured twice for the club this season and is out of match practice.
However, Chelsea are very interested in signing Atletico's star striker Costa in the summer and have been discussing a potential transfer with the La Liga club for the best part of a month.
Some newspapers reported that an agreement had been found over the weekend with the figure believed to be as much as €60m, but El Confidencial reports that, if Courtois is allowed to play in the Champions League, Atletico will allow Costa to leave for slightly less.
Mourinho was reportedly ready to bring Courtois back to Stamford Bridge in favour of dismissing Petr Cech from the number one spot but because Costa is the Special One's number one target, he has began using Courtois as a bargaining chip.
Costa's move to Stamford Bridge may see Courtois spend another season on loan to Atletico instead of deputising in west London for the first time since his transfer in 2011.