Chelsea's own goalkeeper is poised to stand between them and a place in the Champions League final after the 2012 winners were drawn to play Thibaut Courtois' Atletico Madrid.
The 21-year-old Belgium goalkeeper is on loan at Atletico for a third successive season and Chelsea insist he will be free to play against them, in line with UEFA rules, as the clubs compete for a place in the May 24 final in Lisbon against Real Madrid or defending champions Bayern Munich.
It was reported that Chelsea would allow the Spanish side to play the Belgian in both legs of the semi, provided they paid a fee of around 3million euros for each game.
However, UEFA moved to clarify that it expects Courtois to be free to face the Blues in both legs.
Chelsea chief executive Ron Gourlay told chelseafc.com: "The loan was arranged at the start of the season and it is quite simple, Courtois can play against Chelsea, that was never in doubt.
"Regarding the UEFA statement, we will evaluate that over the course of the next 24 or 48 hours and we will comply with the rules, and he can play against Chelsea in both games."
UEFA's statement, made in advance of the draw, read: "The integrity of sporting competition is a fundamental principle for UEFA.
"Both the UEFA Champions League and the UEFA disciplinary regulations contain clear provisions which strictly forbid any club to exert, or attempt to exert, any influence whatsoever over the players that another club may (or may not) field in a match.
"It follows that any provision in a private contract between clubs which might function in such a way as to influence who a club fields in a match is null, void and unenforceable so far as UEFA is concerned.
"Furthermore, any attempt to enforce such a provision would be a clear violation of both the UEFA Champions League and the UEFA disciplinary regulations and would therefore be sanctioned accordingly."
Courtois played against his parent club in the 2012 Super Cup, when Atletico were 4-1 winners. The match also pits Chelsea striker Fernando Torres against his former club.
Jose Mourinho's Chelsea, who beat Paris St Germain on Tuesday night to advance, play in Madrid on April 22, with the return at Stamford Bridge on April 30.
Should Chelsea prevail, Mourinho's men will meet either Real Madrid or Bayern Munich - the side the Blues beat in the 2012 final - in the Portuguese capital next month.
Mourinho had good and bad moments during three years at Real, where he regularly found himself up against Pep Guardiola, now the Bayern boss.
Mourinho has won only three of his 16 meetings with Guardiola, with the most recent encounter coming when Europa League winners Chelsea lost the Super Cup to the Germans in Prague last August.
Real's pairing against Bayern brings together two clubs who have won the competition 14 times between them.
Five-times winners Bayern, quarter-final conquerors of Manchester United, are the defending champions. They beat fellow German side Borussia Dortmund at Wembley last May, and want to become the first team in the Champions League era to defend the European Cup.
Real, who booked their place in the last four with a win over Dortmund, have won European club football's top prize nine times - but not since 2002 - and host the first leg on April 23.
Bayern's chairman Karl-Heinz Rummenigge said on his club's website: "It's going to be a duel that both Bayern and Real fans can look forward to.
"I'm sure Pep (Guardiola)'s looking forward to it too. We're up against one of the best sides in the world, a really great team.
"We respect Real, but we have a big chance of writing history, which would be to defend our title, and we believe in that."
Chelsea's Premier League match with Sunderland, which was scheduled for April 20, has been brought forward to April 19 to give the Blues more preparation time.
The Stamford Bridge clash will kick-off at 17:30BST.