Atletico Madrid goalkeeper Thibaut Courtois will not play in the Champions League semi-final if his side are drawn against Chelsea.
The Belgian stopper is on loan from the Blues, and under the conditions stipulated in his loan agreement, Atletico would have to pay a large sum to Chelsea if Courtois were to appear.
ESPN reports how Enrique Cerezo, the club's president has told Spanish radio Onda Cero that "a large sum of money" - believed to be €6 million (£4.9 million) over both legs - would need to be paid to Chelsea as per a clause added into the two clubs' loan agreement at the start of the season.
UEFA rules prevent players being barred from featuring against other clubs, but European football's governing body are powerless to stop such clauses being inserted into loan agreements.
The 21-year-old is in his third season with the title contenders, having arrived at Chelsea from Belgian side Genk when he was 19.
Atletico would likely be forced to field second choice goalkeeper Dani Aranzubia, 34, who has featured only twice this season.
His first outing was in December's 2-0 Champions League group stage win at home to Porto with Courtois suspended, and Atletico had already qualified for the knockout stages.
His most recent appearance came in February's 2-0 Liga defeat to Almeria - in which he was sent off.
Atletico remain this season's only unbeaten team in the Champions League, and will be hoping that run can continue in the semis regardless of who is in goal.
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