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.
A guide to the Champions League semi-finalists
A guide to the Champions League semi-finalists
1/4 REAL MADRID
Best: Winners (1955, 1956, 1957, 1958, 1959, 1960, 1966, 1998, 2000, 2002)
Star man: Cristiano Ronaldo
Manager: Carlo Ancelotti – has won the league in England, France and Italy, as well as the Champions League twice with Milan, and is now expected to deliver ‘la decima’ – Real Madrid’s tenth European title
Top scorer: Cristiano Ronaldo (14)
Top assist: Karim Benzema/Angel Di Maria (both 5)
Overview: After sailing through the group stages unbeaten, and then dispatching Schalke 9-2 in the last 16, Real Madrid were the form team in the tournament until their scare against Dortmund. The 2-0 defeat in Germany, albeit without their talisman Ronaldo, has revealed a chink in the armour, but you still wouldn’t want to draw them.
Best: Winners (2012)
Star man: Eden Hazard
Manager: Jose Mourinho – The ‘Special One’ is looking to become the first manager to win the competition with three different teams having succeeded at Porto and Inter
Top scorer: Samuel Eto’o/Demba Ba/Fernando Torres (all 3)
Top assist: Oscar (4)
Overview: Despite losing twice to unfancied Basel, Chelsea topped their group and saw off the tricky task of Galatasaray in the last 16. Needed a last minute goal to scrape past PSG in the quarter-final, and will go into the semi-finals as underdogs – as they did in 2012.
3/4 BAYERN MUNICH
Best: Winners (1974, 1975, 1976, 2001, 2013)
Star man: Franck Ribery
Manager: Pep Guardiola – in his first season at Barcelona he won a treble that included the Champions League, and he’s on course to do the same in his first season at Bayern. If he does it his place among the greats will no longer be in doubt.
Top scorer: Thomas Muller (5)
Top assist: Arjen Robben/Phillip Lahm (both 3)
Overview: Aside from a defeat at home to Manchester City, by which stage qualification was already secured, Bayern have been almost perfect, blowing away Arsenal and Manchester United in the knock-out stages. Favourites to become the first team in the Champions League era to retain the title.
4/4 ATLETICO MADRID
Best: Runners-up (1974)
Star man: Diego Costa
Manager: Diego Simeone – the only manager left who was at his club last season, Simeone has built a team performing beyond the resources of Atletico, with a real shot at a first Spanish title since 1996.
Top scorer: Diego Costa (7)
Top assist: Gabi (4)
Overview: Atletico are the only unbeaten team left in the competition, and having seen off Milan and Barcelona they deserve their place in the semi-finals. They may be the only team left never to have won a European title, but they can no longer be considered underdogs, and everyone will want to avoid them.
"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.
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