Chelsea have been drawn to face Atlético Madrid in the Champions League semi-finals, having been told by Uefa that a clause requiring the Spaniards to fork out up to €6m for the goalkeeper Thibaut Courtois to play against his parent club is "null, void and unenforceable".

Unlike in the Premier League, where loan players cannot face their parent clubs, there are no such restrictions in the Champions League. Courtois, who is in his third season on loan at Atlético, played well for the La Liga leaders against Chelsea last season in the Spanish club's European Super Cup victory and, if that was slightly embarrassing for Chelsea, it may have motivated them to insert the clause into Courtois's latest deal.

However, Uefa has now stepped in and warned Chelsea they will face disciplinary proceedings should they attempt to make Atlético pay the sum, despite the contractual position.

It remains to be seen whether Atlético would select Courtois and risk damaging relations with Chelsea, given they want to take the 21-year-old back on loan next season. Chelsea are also known to be prioritising the signing of Atlético's striker Diego Costa.