Guardiola has been in charge almost three years; but there can only be one winner in Spain. If Mourinho is to succeed then it means that Guardiola must be failing.
Pressure starts now on Barcelona coach Pep Guardiola
Pep Guardiola, the Barcelona manager is usually described in endearing terms. Effortlessly cool, calm and collected, he can converse in four languages and cuts a figure of sartorial perfection.
Catalan men want to be Guardiola, women want to be with him. Barca's boss usually talks on his terms - from a position of power. He can afford to be magnanimous in his praise because his charges are so good.
He does not do one-on-one interviews so as not to appear to favour one media outlet over another. The 40-year-old is a man in control, yet he is also human and can succumb to pressure like anyone. And there is lots of pressure when you are in charge at Barca.
Raul, the Real Madrid legend who will face Manchester United for Schalke 04 tonight, said: "Look at Pep Guardiola: he's done brilliantly but he'll last, what, a year longer? [Jose]Mourinho will be at Madrid for three or four years, I'd imagine. It's not easy. You need patience."
Raul was talking about the longevity of coaches in Spain compared with other major European football nations.
"There isn't the same culture here," he said. "As soon as objectives go unfulfilled, the project suffers. But I think Madrid have now found the key person in Jose Mourinho. He will be there for as long as he wants, whether that's two, three, or four years. In Spain, any longer is hard."
Guardiola has been in charge almost three years; but there can only be one winner in Spain. If Mourinho is to succeed then it means that Guardiola must be failing. Second is not good enough.
Barca have employed 12 different coaches since Sir Alex Ferguson took control of Manchester United in 1986, Real Madrid 25. Johann Cruyff was in charge for eight years, Frank Rijkaard five. Both lost their jobs within months of the form of their team starting to dip.
There is little evidence to suggest that Barca are anything other than the best team in the world, but things have not been going Guardiola's way in the last week. Defeat to Real in the Copa Del Rey final in Valencia has shaken Barca's domestic pre-eminence.
Over the next 10 days, Guardiola will face the biggest challenge to his hegemony of Spanish football. He predicted on Saturday that: "Madrid won't lose another league game. I know what it is to play after winning a trophy. They feel freed."
They certainly looked that way when a Real second string demolished Valencia 6-3 in their now favourite hunting ground of the Mestalla on Saturday.
Three hundred kilometres up the Mediterranean coast, Guardiola was not his usual self in the press conference following Barca's 2-0 victory over Osasuna with a much-changed side.
Both giants are saving players for the biggest battles, but Lionel Messi did score his 50th goal of the season and David Villa ended his goal drought.
Yet Guardiola was tense and agitated. Nothing obvious, but there was a shift. A question in Spanish was answered in Catalan. Then he said: "It seems few people are still behind us but I believe in the strength, the spirit and the honour of this team."
Did he seriously believe some people had lost their respect for his team after just one defeat?
"We accept that Madrid will be favourites in the Champions League," Guardiola said about the semi-final first leg, generating considerable surprise.
"They deserve that after their performances of the past few weeks, but we'll try to change that."
Spain remains engrossed. The king isn't dead, nowhere near. Barca have won the league, but lost a cup final.
They face a bigger battle starting on Wednesday in the Bernabeu, but Guardiola's subjects wonder how he will react if his side are eliminated by Real and he has to face a relative crisis for the first time as Barca coach.