Pep Guardiola looked up, asked which was José Mourinho's camera and began. "You called me Pep, so I'm going to call you José," he said, staring straight down the lens. It was the eve of the Champions League semi-final and he said a lot more besides, declaring Mourinho the "fucking man" and insisting he would let the Real Madrid coach have his "own little Champions League" for media stirring. He, on the other hand, would try to win the actual Champions League. Like a school kid calling out his rival, he declared: "See you on the pitch, tomorrow night at 7.45."

After almost three years of impeccable, almost exaggerated politeness this was a new departure. Mourinho, the mind games master, had really got under his skin, finally provoking a nervous breakdown. Guardiola was no longer in control, it was claimed. In fact, he had planned the response. His discourse was deliberate. He had decided that it was the message his players needed to hear. He had felt good doing it too – liberated, infused with renewed energy. When he arrived at the team hotel, his players gave him a standing ovation. The following night, they beat Real Madrid 2-0. Guardiola was the winner.

For now, at least. If the response was planned, the impression was not completely wrong. Mourinho is not the sole cause but the pressure on the Barcelona coach, often self-imposed, is very real. His assistants complain that he hardly eats. He complains that he is getting old and losing patience. Asked if he would like greater responsibility, Guardiola protested: "But I've already got a bad back and I'm losing my hair!" Before the semi-final second leg he declared the series of four clásicos, "18 extremely hard days".

Eighteen days? It has been an extremely hard season in which Guardiola has felt unprotected, has suffered a slipped disc and been taken into hospital. Eric Abidal has been diagnosed with a tumour. And then there's Mourinho – constantly chipping away with the aid of the media. One radio station even accused Barcelona's players of doping. Guardiola believed the leak was strategic, talking of the "milk-board" – those journalists working more for Real Madrid than their media.

A coach who always dismissed emulating Sir Alex Ferguson as "impossible", Guardiola could have been forgiven for being tempted to walk. Success on Saturday would allow him to do so closing a triumphant cycle. A second European Cup would eclipse the Dream Team. Winning at Wembley, where he played 19 years ago, would emulate them. In April, an Italian TV station broadcast images of Guardiola admitting that his time at Barcelona was "nearing an end".

"Next year," he said, "would be my fourth. You have to know when to walk: players get tired of the coach and the coach gets tired of the players." Barcelona insisted that Guardiola was only saying what he had always insisted. Every year he signs a single-year extension to his contract. He says he would sign six-month deals if he could. When Mourinho said Barcelona should give him a fifty-year contract, he sighed: "Mr Mourinho really doesn't love me."

Those close to him say Guardiola has at least a year left at Barcelona, probably followed by a sabbatical. If and when he goes there will be a queue at the door of a coach who speaks good English and is fond of the UK, London especially. A coach who has said: "I never got the chance to play in England. I wouldn't rule it out [as a manager] but nor am I contemplating it now." This is a man who left Barcelona once before and, one day, will do so again.

For potential employers, doubts remain. Few would argue that Guardiola has not had a central role at Barcelona, however insistent he is on solely crediting his players. It is not just about sticking Messi on the pitch.

When Guardiola arrived Madrid had finished 18 points ahead: since then, he has won three successive league titles, a Champions League and a Copa del Rey. Win on Saturday and he would be Barcelona's most successful coach. His work has been exceptional. But the question lingers, is it for export?

Guardiola was Barcelona ballboy, Barcelona captain and Barcelona youth team coach before taking over. One collaborator says he "suckled at the teat of Johan Cruyff" – Barcelona's ideological founder, a kind of guru. His commitment to the model and style is non-negotiable. Zlatan Ibrahimovic bitterly called him "the philosopher".

And yet the notion of Pep the puritan is skewed, ignoring the pragmatism and the seductive character, the skills and simplicity of the message. "If Pep told me to throw myself off the second tier at the Camp Nou," says Dani Alves, "I'd think: 'There must be something good down there.'" Not only is he flexible and resourceful, but for Guardiola – who once warned a referee he was "playing with the emotions of a country" [Catalonia] – working elsewhere might even prove a liberation.

"When they signed Guardiola, I said, Madre mía, we're going to be flying," says Xavi. "I'm sure Pep would succeed anywhere. Intelligence is often expressed in how well you adapt to where you are, to your circumstances. And he is very, very intelligent. He would adapt to any football anywhere. He is a perfectionist, obsessive: he keeps going until he gets it right, no matter what he's doing. If Pep Guardiola decided to be a musician, he would be a good musician. If he wanted to be a psychologist, he would be a good psychologist."