Nyon - Title-holders Bayern Munich will face nine-time winners Real Madrid in a dramatic Champions League semi-final, which was drawn on Friday.
GALLERY: Champions League semi-final draw
Surprise packages Atletico Madrid must take on 2012 winners Chelsea in the second semi-final with goalkeeper Thibaut Courtois at the centre of a contractual intrigue between the two sides.
Bayern, who knocked out Manchester United on Wednesday, are aiming to become the first club to successfully defend the trophy in the 22-season Champions League era.
Bayern captain Philipp Lahm said the two leg clash should be the tournament final.
"The top two teams will play each other.
"These games are worthy of being the final. You only have one goal when you are in the semi-final - to reach the final at all costs," said Lahm.
Real coach Carlo Ancelotti forecast "a very difficult tie for us, but also for Bayern Munich".
The Italian added: "I think Bayern Munich are a great team. They have individual and collective quality and have had a great season.
"Pep Guardiola is one of the best coaches in the world and has a lot of experience.
"Bayern Munich could be the favourites, but our objective is to win the Champions league and if we want to win it we have to beat Bayern Munich."
Guardiola's German champions met Real in the semi-finals in 2011/12. They won that match on penalties in Madrid before losing to Chelsea in the final.
The continental superpowers have met five times in the semi-finals in all, with Bayern winning four.
While Bayern, seeking their sixth European trophy, are trying to reach their fourth final in five years Atletico are aiming to make it to their second, having been beaten by Bayern in the 1974 climax.
The La Liga leaders' reward for their stunning victory over Barcelona in the quarter-finals is a match up against former Real boss Jose Mourinho's Chelsea.
The pair last met in the 2012 Super Cup with Atletico beating Chelsea 4-1.
Mourinho is trying to win the coveted title for a third time with different clubs after Porto and Inter Milan.
Before the draw, UEFA made a veiled warning to Chelsea that they must not stop Atletico using goalkeeper Courtois.
European football's governing body said any provision in Courtois' loan agreement preventing his participation is against the competition's rules.
"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," European football's governing body said in a statement.
"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."
Courtois has been a key player in Atletico's spectacular season. Atletico beat Barcelona on Wednesday to qualify for the semi-finals for the first time in 40 years.
Atletico president Enrique Cerezo told Spanish radio station Onda Cero after the match however that his side would have to pay "a lot of money" for the Belgian international to face Chelsea due to a provision in his contract.
Spanish media reports estimated the fee to be three million euros per match.
Courtois faced Chelsea once as an Atletico player in the European Supercup last season when the Spaniards ran out 4-1 victors.
Chelsea chief executive Ron Gourlay however later insisted there was no dispute.
"The loan was arranged at the start of the season. He could play against Chelsea - that was never in doubt," he told Sky News.
On the semi-final clash he added: "They're all fantastic sides. The important thing to us was to make sure we were in the semi-final.
"We need to make sure we are totally prepared for these games. I'm sure Jose will make sure we are but we have some important games before that."
The Champions League first legs are on April 22/23 with the return legs on April 29/30. The final is in Lisbon on May 24.
The Europa League semi-final draw pitted Spanish duo Sevilla and Valencia against each other. The other semi-final sees Benfica of Portugal play Juventus of Italy with the semi-finals to be played on April 24 and May 1.