We could all see that Pep Guardiola's Barcelona were brilliant. What's harder is understanding how they did it. That's where my friend Albert Capellas comes in. Whenever he and I run into each other, we talk about Barça. Not many people know the subject better. Capellas is now the assistant manager at Vitesse Arnhem in the Netherlands but before that he was coordinator of Barcelona's great youth academy, La Masia. He helped bring Sergio Busquets from a rough local neighbourhood to Barça. He trained Andrès Iniesta and Victor Valdes in their youth teams. In all, Capellas spent nine years working for his hometown club. 

During our last conversation, over espressos in an Arnhem hotel last year, I had several "Aha" moments. I had watched the Barcelona of the Pep Guardiola years umpteen times, but only then did I finally begin to see. Guardiola's Barcelona were great not merely because they had great players. They also had great tactics — different not just from any other team today, but also different from Barcelona teams pre-Guardiola. Barça were so drilled on the field that in some ways they are more like an American football team than a soccer one. Their luscious game wasn't nearly as spontaneous as it looked. 

Before getting into the detail of their style, it's crucial to understand just how much of it came from Guardiola. When a Barcelona vice-president mused to me five years ago that she'd like to see the then 37-year-old Pep be made head coach, I never imagined it would happen. Guardiola was practically a novice. The only side he had ever coached was Barça's second team. However, people in the club who had worked with him — men like the club's then president Joan Laporta, and the then director of football Txiki Beguiristain — had already clocked him as special. Not only did Guardiola know Barcelona's house style inside out, he also knew how it could be improved.

Guardiola once compared Barcelona's style to a cathedral. Johan Cruyff, he said, as Barça's supreme player in the 1970s and later as coach, had built the cathedral. The task of those who came afterwards was to renovate and update it. Guardiola was always looking for updates. If a random person in the street says something interesting about the game, Guardiola listens. He thinks about football all the time. He learned from another Dutch Barcelona manager, Louis van Gaal, but also from his years playing for Brescia and Roma in Italy, the country that pretty much invented defending. Yet because Guardiola had little desire to explain his ideas to the media, you end up watching Barça without a codebook. 

Cruyff was the single most formative influence on Guardiola. When the Dutchman returned to the Nou Camp as head coach in 1988, he did something that few Barça coaches had ever done before: he went to the pitches where the youth teams played. There he saw a skinny kid in central midfield hitting perfect passes. "Take that boy off at half-time," he told the boy's coach. "Why?" asked the coach. "Because I'm putting him in the first team," said Cruyff. Guardiola went on to spend a decade in the first team.

Cruyff was perhaps the most original thinker in football's history, but most of his thinking was about attack. He liked to say that he didn't mind conceding three goals, as long as Barça scored five. Well, Guardiola also wanted to score five, but he minded conceding even one. If Barcelona is a cathedral, Guardiola added the buttresses. Even in his last, somewhat disappointing, season as coach, they conceded only 29 goals in 38 league games. Sir Alex Ferguson's assistant manager at Manchester United, René Meulensteen, told the Dutch magazine Voetbal International, "Pep Guardiola's Barcelona made the biggest change at the top of football, and I'm especially talking about how they played without the ball. They applied very fast and coordinated pressure to win back the ball as quickly as possible." There were four key Guardiola tenets: 

Pressure on the ball

Before Barcelona played Manchester United in the Champions League final at Wembley in 2011, Alex Ferguson said that the way Barça pressured their opponents to win the ball back was "breathtaking". That, he added, was Guardiola's innovation. Ferguson admitted that United hadn't known how to cope with it in the Champions League final in Rome in 2009. He thought it would be different at Wembley. It wasn't. 

Barcelona start pressing the instant they lose possession. That is the perfect time to press because the opposing player who has just won the ball is vulnerable. He has had to take his eyes off the game to make his tackle or interception and he has expended energy. That means he is unsighted and probably tired. He usually needs two or three seconds to regain his vision of the field. So Barcelona try to dispossess him before he can give the ball to a better-placed teammate. 

Furthermore, if the opponent won the ball back in his own defence, and Barcelona can instantly win it back again, then the way to goal is often clear. This is where Messi's genius for tackling comes in. The Argentinian has such quick reflexes that he sometimes wins a tackle a split-second after losing one.

The Barcelona player who lost the ball leads the hunt to regain it. But he never hunts alone. His teammates near the ball join him. If only one or two Barça players are pressing, it's too easy for the opponent to pass around them. Meulensteen said, "You see that few teams have the individual skills to play themselves out from under pressure. Guardiola saw that very well. But Barcelona's is also the playing style with the highest degree of difficulty. You need players with the tactical qualities to shift very quickly from possession to defence, and who are physically capable of doing that constantly. It's a very short moment of hunting the prey."

The "five-second rule"

If Barça haven't won the ball back within five seconds of losing it, they then retreat and build a compact 10-man wall. The distance between the front man in the wall (typically Messi) and their last defender (Javier Mascherano, say) is only 25 to 30 metres. It's hard for any opponent to pass their way through such a small space. The Rome final of 2009 was a perfect demonstration of Barcelona's wall: whenever United won the ball and kept it, they faced 11 precisely positioned opponents, who stood there and said, in effect: "Try to get through this."

It's easy for Barcelona to be compact, both when pressing and when drawing up their wall, because their players spend most of the game very near each other. Xavi and Iniesta in particular seldom stray far from the ball. A packed midfield, with no out-and-out strikers, enhances the compactness. Cruyff has said, "Do you know how Barcelona win the ball back so quickly? It's because they don't have to run back more than 10 metres as they never pass the ball more than 10 metres." 

More rules of pressing: once Barcelona have built their compact wall, they wait for the right moment to start pressing again. They don't choose the moment on instinct. Rather, there are very precise prompts that tell them when to press. One is if an opponent miscontrols a ball. If the ball bounces off his foot, he will need to look downwards to locate it and at that moment he loses his overview of the pitch. That's when the nearest Barcelona players start hounding him. 

There's another prompt for Barça to press: when the opposing player on the ball turns back towards his own goal. When he does that, he narrows his options: he can no longer pass forward, unless Barcelona give him time to turn around again. Barcelona don't give him time. Their players instantly hound the man, forcing him to pass back, and so they gain territory.

The "3-1 rule"

If an opposing player gets the ball anywhere near Barcelona's penalty area, then Barça go Italian. They apply what they call the "3-1 rule": one of Barcelona's four defenders will advance to tackle the man with the ball, and the other three defenders will assemble in a ring about two or three metres behind the tackler. That provides a double layer of protection. Guardiola picked this rule up in Italy. It's such a simple yet effective idea that you wonder why all top teams don't use it.

No surprises. When Barcelona win the ball, they do something unusual. Most leading teams treat the moment the ball changes hands — "turnover", as it's called in basketball — as decisive. At that moment, the opponents are usually out of position and so if you can counterattack quickly, you have an excellent chance of scoring. Teams like Manchester United and Arsenal often try to score in the first three seconds after winning possession. So their player who wins the ball often tries to hit an instant splitting pass. Holland — Barcelona's historical role models — do this too.

But when a Barcelona player wins the ball, he doesn't try for a splitting pass. The club's attitude is: he has won the ball, that's a wonderful achievement and he doesn't need to do anything else special. All he is supposed to do is slot the ball simply into the feet of the nearest teammate. Barcelona's logic is that in winning the ball, a player has typically forfeited his vision of the field. So he is the worst-placed player to hit a telling ball. This means that Barcelona don't rely on the element of surprise. They take a few moments to get into formation, and then pretty much tell their opponents, "OK, here we come." The opposition knows exactly what Barça are going to do. The difficulty is stopping it.

The only exception to this rule is if the Barça player wins the ball near the opposition's penalty area. Then he goes straight for goal.

Possession is nine-tenths of the game. Keeping the ball has been Barcelona's key tactic since Cruyff's day. Most teams don't worry about possession. They know you can have oodles of possession and lose. But Barcelona aim to have 65-70% of possession in a game. In the 2011-2012 league season, they averaged more than 72%. 

The advantage of possession is twofold. Firstly, while you have the ball, the other team can't score. A team like Barcelona, short on good tacklers, needs to defend by keeping possession. As Guardiola once remarked, they are a "horrible" team without the ball. Secondly, if Barça have the ball, the other team has to chase it, and that is exhausting. When the opponents win it back, they are often so tired that they surrender it again immediately. Possession gets Barcelona into a virtuous cycle.

Barça are so fanatical about possession that a defender like Gerald Piqué will weave the most intricate passes inside his own penalty area rather than boot the ball away. In almost all other teams, the keeper at least is free to boot. In the England side, for instance, it's typically Joe Hart who gives the ball away with a blind punt. This is a weakness of England's game, but the English attitude seems to be that there is nothing to be done about it: keepers can't pass. Barcelona think differently.

José Mourinho, Barcelona's nemesis, tried to exploit their devotion to passing. In the Bernabéu in December 2011, Real Madrid's forwards chased down Valdes from the game's first kick-off, knowing he wouldn't boot the ball clear. The keeper miscued a pass and Karim Benzema scored after 23 seconds. Yet Valdes kept passing and Barcelona won 3-1. The trademark of Barcelona-raised goalkeepers — one shared only by Ajax-raised goalkeepers, like Edwin van der Sar — is that they can all play football like outfield players. That characteristic will be key in Barça's hunt for Valdes's successor. The club may well choose to sacrifice core keeping skills in favour of ball-playing ability.

The "one-second rule"

No other football team plays the Barcelona way. That's a strength, but it's also a weakness. It makes it very hard for Barça to integrate outsiders into the team, because they struggle to learn the system. Barcelona long had a policy of buying only 'Top 10' players — men who arguably rank among the 10 best footballers on earth — yet many of them have failed in the Nou Camp. Thierry Henry and Zlatan Ibrahimović did, while even David Villa, who knew Barcelona's game from playing it with Spain, has often found himself on the bench.

Joan Oliver, Barcelona's previous chief executive, explained the risk of transfers by what he called the "one-second rule". The success of a move on the pitch is decided in less than a second. If a player needs a few extra fractions of a second to work out where his teammate is going, because he doesn't know his teammate's game well, the move will usually break down. A new player can therefore lose you a match in under a second. 

That's particularly true at Barcelona, whose system has such a complex orchestration. Soon after Cesc Fabregàs returned home from Arsenal, he said, "Barça have a very specific system and everyone has to adjust to it. Everything has been studied down to the last millimetre. In my first matches I really had to adjust. I was so used to Arsenal, where I could roam around the whole pitch without worrying about anything. Here it's really very different. Everyone has his own position and you can never lose it from sight. I had to go back to my youth days at Barça to master the basic principles again." 

Barcelona needed Fabregàs precisely because he had once mastered those basic principles. An even better example of this staffing principle is Pedro: not a great footballer, but because he was raised in La Masia he can play Barcelona's game better than stars from outside. The boys in La Masia spend much of their childhood playing passing games, especially Cruyff's favorite, six against three. Football, Cruyff once said, is choreography.

Nobody else thinks like that. That's why most of the Barcelona side is homegrown. It's more a necessity than a choice. Still, most of the time it works pretty well. 

No doubt Guardiola will want to transplant most of this system — plus new ideas he has thought up in Manhattan — to Bayern Munich. But in a team that grew up without these principles, such a complex knowledge transfer could easily fail.