There will be no call made to Pep Guardiola after the coach's former club Barcelona were drawn against his future club Bayern Munich in the Champions League semi-finals. A potential clásico between Barça and Real Madrid, who have been pitted against Borussia Dortmund, will have to wait until Wembley but getting there will not be easy for either side, even if Bayern do not have the advantage of insider information.

"On the one hand, Jupp [Heynckes] is still the coach of Bayern and Pep does not arrive until June," Matthias Sammer, Bayern's sporting director, said. "On the other, it is a matter of respect: this is an ethical question."

For Guardiola the draw is a fascinating and potentially uncomfortable one: the side he constructed against the side he is about to join at a time when theoretically he is still occupying neutral territory. The question inevitably being asked is: who will Guardiola support?

"Pep's semi", as one Spanish newspaper called it, is just one of a host of fascinating story lines to emerge from the draw in Nyon. That the final is at Wembley makes it special for Barcelona; it was there that they won their first European Cup in 1992 and they also claimed the trophy there in 2011. Andoni Zubizarreta, Barça's sporting director, called it a "magical" place. They are unbeaten in their past 17 games against German clubs.

For Madrid there is the pursuit of the decima, the 10th European Cup – they have now been waiting a decade. It has become an obsession. They waited 32 years for the seventh, winning it in 1998 – beating the holders Dortmund en route during a game that was famous for fans pulling down the goalposts. Bayern have the added motivation of being last year's traumatised, beaten finalists at their own ground, the Allianz Arena.

There could hardly be a stronger line-up. Barcelona have reached six successive semi-finals, a European Cup record, and won the competition in 2009 and 2011; Bayern finished runners-up in 2010 and 2012; Madrid have reached three semi-finals in a row under José Mourinho, the coach seeking a unique third triumph with a third different club. Between them the four clubs have a remarkable 18 European Cups.

Dortmund may appear to be the odd one out but they have been hugely impressive this season – even if it did take an astonishing comeback against Málaga to go through. Few would argue against judging these four to be the tournament's best teams and while at the semi-final stage last season Madrid and Barcelona seemed destined to reach the final, this time that is not the case.

Emilio Butragueño, the Madrid director and former striker, said: "We have played Dortmund twice and not been able to beat them."

Even before the competition began Mourinho insisted that Dortmund were candidates and when they met Madrid in the group stages they were the better side – twice. Dortmund defeated Madrid 2-1 in Germany and drew 2-2 at the Santiago Bernabéu.

"I'm happy to finally know which team we are going up against," said Jürgen Klopp, the Dortmund manager. "I don't need to stress the fact that Real Madrid will be a tough opponent. But they are the only team that was left in the draw whom we've managed to beat this season already."

On the other side of the draw, Uli Hoeness, the Bayern president, said: "Barcelona are favourites but they have lost their aura."

The last time Bayern and Barcelona met in the Champions League was in the 2009 quarter-finals and Barcelona won 4-0 at the Camp Nou. "I remember that by the end I didn't want to watch any more," said Karl-Heinz Rummenigge, Bayern's chief executive. "But I think we have a good chance to show how we have progressed since 2009."

Although a meeting between Bayern Munich and Real Madrid – that other great European rivalry – has been avoided, this is a continuation of a struggle for supremacy that is unfolding more generally between Spanish and German football.

The semi-finals bring together the German and Spanish champions from 2011-12 and, barring a miracle, the German and Spanish champions from this year. This season the statistics favour the Germans: in six Champions League meetings German clubs have won three times against Spanish opposition and drawn three times.

"German and Spanish teams are clearly the strongest in the continent at the moment," Hoeness said. "It is not coincidence that they have four teams in the semi-finals. Right now, the Italians cannot compete."