A Romanian named Helmuth Duckadam later ruined everything but on the night of 16 April, 1986 the greatest failure in FC Barcelona's history was still three weeks away and as improbable as what had just joyously unfolded at Camp Nou. Barça had overturned a 3–0 first-leg deficit in the European Cup semi-final with IFK Gothenburg thanks to a hat-trick from the third-choice striker Pichi Alonso, before their goalkeeper Javi Urruti took the shoot-out into sudden death by saving one penalty and scoring another.

Then Víctor Muñoz's strike sent them to their second ever final. As Muñoz celebrated, a delirious 15-year-old ballboy in a Barça tracksuit sprinted over, grabbed him by the arm and pleaded for his shirt.

He never did get it, but he got 379 of his own. Tonight he attends another European Cup semi-final but the experience will be different. That night Josep Guardiola i Sala was a Barcelona ballboy; 11 years later he was made Barcelona's captain; 11 years after that he became Barcelona's coach.

Guardiola was slow, rarely scored goals and insisted that but for Johan Cruyff he would never have escaped the Third Division. But he won six league titles, a European Cup and Olympic gold. Born in the Catalan town of Santpedor, schooled barely 100 metres from Camp Nou and resident at La Masia, the traditional farmhouse that stands incongruously in its shadow, he was the metronome at the heart of the finest side Barcelona produced, ordering, constructing, constantly moving the ball. The midfielder an opponent described in a single word: "pam". "Pam-pam-pam-pam-pam-pam-pam-pam". As if that was not enough, he was also an intelligent and impassioned defender of Catalan culture, language and identity.

It is hardly surprising that Andrés Iniesta admits he pinned up Guardiola posters, or that when Guardiola became coach last summer he was granted the benefit of the doubt. The trouble was, there were doubts. Goodwill couldn't disguise the apprehension. Guardiola had won the Third Division with Barcelona B, but he was only 37; it was his first ever season coaching.

Barcelona had finished 18 points behind Real Madrid the previous year. The diagnosis pointed to a cancer: laziness gripped, players were divas, cruising. Few embodied the problem like Ronaldinho, whose belly was expanding as steadily as his performances declined; few were blamed like the coach, Frank Rijkaard, whose laid-back style let it happen. Barcelona needed licking into shape; they needed guarantees. Barcelona needed Mourinho, not some inexperienced novice. Even the president, Joan Laporta, described the Portuguese as the "safe option".

Instead, he chose Guardiola. The Catalan newspaper El Mundo Deportivo published what Barça could have won: the starting XI Mourinho supposedly demanded, salt to rub into Barça wounds when the club that rejected the Special One inevitably hit the rocks. And hit the rocks they duly did, collecting a solitary point in their opening two matches, their worst ever start. The club duly collected a solitary point from Guardiola's first two matches, their worst ever start.

"Guardiola was the world's worst coach," cackles former striker Hristo Stoichkov, who played with him. "Now what?" Now, they think he's a genius. As Laporta insists: "Lots of people now claim to have recommended Pep but the reality was quite the reverse." People who knew him knew what he could bring. "Even at La Masia he was known as The Wise One," recalls the former player and coach Charly Rexach. One of Guardiola's closest collaborators insists: "Those who said he had no experience are idiots: Pep was a coach when he played. Experience isn't things happening to you, it's learning, seeking solutions."

He certainly found solutions. He imposed discipline, with fines of €6,000 for being late to training, €500 for missing breakfast with the squad. He sold Ronaldinho and Deco, won over those who stayed with a combination of tough demands and bright psychological management, and brought knowhow, perfectionism and seriousness – right down to weaning Leo Messi off pizza, steak and Coke.

His analysis is exhaustive; its presentation digestible. Videos were unheard of last season; now they are standard. The detail is striking, its application sharp and to the point. "He remembers everything," says Xavi. "And everything's done for a reason." Results bear him out: top of La Liga and in the final of the Copa del Rey, Barcelona could yet win the ­treble. But it is not results that have made Guardiola an even greater idol; it is the way his side gets them.

Bobby Robson could not win even when he won. His Barcelona side took the Cup Winners' Cup, the Cup and the Spanish Super Cup in 1996-97. They finished second, two points behind Madrid, and scored a club-record 102 league goals. But he was treated like a loser.

"In England, I'd be a bloody hero," Robson complained. "Sometimes I ask myself why everybody has it in for me." The answer was simple: Robson was not Johan Cruyff and his Barça were not the Dream Team.

More than just a team that won four successive league titles between 1991 and 1994 and the European Cup, the Dream Team were an ideal, a model of touch, technique and movement. Cruyff gave Barcelona an unshakeable identity that runs right through the club, one whose roots are in the Ajax school and Dutch Total Football. "Show me 20 kids in a park and I can tell which are at Barcelona," insists one pundit. The model was embodied, above all, by Guardiola and is traceable through Xavi Hernández, Iniesta and even Cesc Fábregas. Xavi describes himself as a "child of the system"; Iniesta recalls the message: "receive, pass, offer, receive, pass, offer." The first time he saw Iniesta, Guardiola – by then a veteran – told Xavi: "You're going to retire me; he's going to retire us all."

He may have departed as a player but Guardiola's commitment to the Dream Team's ideal remained deep. One colleague says he has "suckled from the teat of ­Cruyff" and that was what brought him back as coach. As Laporta, advised by Cruyff, admits, Guardiola contrasted with the self-promoter Mourinho. "We chose a philosophy, not a brand," Laporta says. "Guardiola knows the club and he is part of its ­history. He represents continuity with Cruyff's model." "Pep knows Barcelona better than anyone," says Rexach. "It's all about the Dream Team," adds Eusebio, Barcelona's assistant coach last season.

Even Guardiola admits: "We are sons of the Dream Team, trying to emulate them." Evidence comes in the exaltation of intelligence, positioning and possession, in pressuring opponents high, the non-negotiable collective commitment to slick attack. Not just to scoring goals – Barcelona have 136 this season – but to building them. Leo Messi is the Champions League's top scorer yet 33 players have taken more shots. This team walks the ball into the net.

For those coaches, like Robson, that followed Cruyff, the Dream Team was the Sword of Damocles, a mythologised image of perfection that subsequent sides could not live up to. Until now. Guardiola has not just emulated the Dream Team; according to Josep Lluís Nuñez, president between 1978 and 2000, he has "bettered" it. The declaration is premature but it speaks volumes. In the Catalan capital there is no greater compliment. Guardiola knows that better than anyone else.