You've got to admire their balls. Real Madrid screeched after them: an entire herd, powerful and co-ordinated, salivating and breathing hard, murder in their eyes. So Barcelona moved the ball on, away from them. Forced back, it was played into Víctor Valdés, the goalkeeper, who slotted it to Carles Puyol, who gave it back again. And that's where it went wrong. Valdés turned and looked to the left, curling his pass straight to Angel Di María. Eric Abidal looked on in horror, powerless; he had opened the pitch out to receive the pass, not closed it to prevent the goal. Sergio Busquets dived in but couldn't stop it happening. One rebound, two, and the ball was in the net.

It hadn't yet been in Madrid's half. Barcelona took the kick off but Madrid took the lead. Valdés sat and thought about what he had done. And, boy, had he done it. Twenty-three seconds and he had gifted Madrid the opening goal. Not just any opening goal, either: the first in the world's biggest rivalry, one that sent tectonic plates crashing into each other. Madrid, so deadly on the counter, so imperious, a goal up (it had been almost 70 games since they'd taken the lead and failed to win), were winning. Victory would effectively put them nine points clear*, the league within reach four years on. Power shifted, Barcelona's era drew closer to its close.

And all because he'd refused to just hoof the bloody thing. Madrid had been preparing this game for months. They were stronger this time and they were ready. Barcelona had been beset by doubts. Now trailing, you could forgive them for being terrified. The last time they'd been in the city, Getafe had beaten them. Fifteen successive Madrid wins looked like becoming 16 – and this one felt decisive. The pressure built, fear too; the consequences were dire. That noise you could hear was knives being sharpened. Valdés was going to get slaughtered.

So what did he do the next time the ball came towards him, accompanied by the charge of the white brigade? He controlled it and picked out his pass, of course.

Voice broken, it was past midnight when Pep Guardiola appeared in the Santiago Bernabéu press room. His players had danced round the dressing room in a big circle, now they were dashing off to Japan. First, a few words. "The perfect image of this game was that after the goal Víctor Valdés continued playing the ball," Guardiola said. "Real Madrid steam-roller you. Most goalkeepers would boot it. But Víctor kept playing the ball. I prefer us to lose the ball like that but give continuity to our play." Valdés, he concluded, "had shown commitment to our approach". "The key was not forgetting our philosophy," said Xavi Hernández. "We don't know how to play any other way – and Victor was brave."

Talk of "philosophy" implicitly imbues it with a kind of moral superiority that tends to irritate but they had a point. And it was not just Valdés; it was Barcelona. After the goal, Dani Alves spoke to his goalkeeper. So did Puyol. There was no ranting, no waving at row Z, no effing and blinding, no crapping in the milk or the consecrated bread, no boot it, you moron. Puyol has now gone 44 consecutive games unbeaten – he was absent in each of Barça's past seven defeats – and here was a small glimpse of why. The captain didn't tell Valdés to get rid of it. Nor did he vow not to give the ball to him. The comedy error gave way to a simple message: Carry On, Víctor.

When people talk of bravery in football, they tend to conjure up Terry Butcher's bandage. The image of bravery is of the hardnut centre-back flying into lunatic challenges. But it's tempting to conclude that that's not brave at all – surely kicking people is the opposite – and even if it is, there's another type of bravery. The player who keeps his head when all around others are losing theirs, who stays strong after a mistake, who overcomes the pressure. A brave player is the one who loses the ball three times and still wants it; who keeps attacking. The goalkeeper who makes the biggest mistake on earth – and doesn't take the easy, if short term, way out. The team that have the courage of their convictions.

Few teams' convictions are as strong as this team's. Barcelona did what Barcelona do, and that includes Valdés. According to the statistical geniuses at Opta Spain, this season only two teams have passed the ball back to the goalkeeper more and Valdés has been given the ball almost 50 times more than Iker Casillas. For most teams, a back pass is a last resort, a release – a panicked prelude to a punt. For Barcelona it is different. Valdés is a player, let him play. His passing accuracy, at 85%, is easily the best in the league – not least because he actually passes it. He attempts fewer long 'passes' (over 35 yards) than anyone, at only 29%. Casillas is the nearest at 43.3% and only three goalkeepers are even under 50%.

So Valdés passed the ball. And so did Barcelona. Even as Madrid pressured high, Barcelona continued to take risks – not taking them is riskier yet; for Barça, a big hoof just means the ball comes back again, at the opposition's feet – and bit by bit they got into the game.

Sure there were moments and Mourinho's talk of fortune was not entirely absurd: Cristiano Ronaldo has been taking an exaggeratedly unfair beating in the media for another big game gone missing, largely because he missed a great chance at 1-0 and a simple header in the second half; Kaká's shot squirmed just wide; and Xavi's goal was a fluke. Barcelona also had Leo Messi to thank for pulling them back into the game – first with the sixth-minute run that sent the first wave of panic through Madrid's minds and then with the astonishing assist for the equaliser. Messi may even have been a little fortunate to avoid a sending off before half-time (although it would have been an extremely harsh red, comprised of two petty yellows) and it is impossible to know what might have happened without the 2-1. But ultimately Barcelona took control.

Although there are still doubts, although they still do not look as fluid or as fresh, and although Guardiola admitted that he did not like the fact that they gave the ball away more than normal, Barcelona mostly did it their way. They left three at the back, flooded the midfield, opened up the pitch – Alves right, Andrés Iniesta left – got hold of the ball and kept it. When Madrid came at them they did not hide, and when they were able to ride the first wave of pressure – at times Madrid's formation was almost a 4-2-4 – they found the pitch opening out before them. By the end, a 4-1 was closer than a 3-2; the sense of superiority, if skewed by then, if exaggerated, was striking.

Barcelona completed 681 passes to Madrid's 427. People say: ah, but how many of those passes are relevant? The answer is: all of them. The pass is Barcelona's identity; it is through possession that they feel comfortable and it is through possession that they do everything – from creating chances to preventing them, from speeding up the game to slowing it down. Even time wasting, even resting, happens with the ball. Possession is aesthetic but also anaesthetic.

They said Madrid were an excellent team – and they are – but by the end they didn't look like one. Just as Manchester United didn't look like one. Twice. Beating everyone else is one thing; Barcelona are a different proposition. And there was a familiarity about that: in the buildup to the 5-0 last season Madrid had won 10 of their past 11 and they came into the famous 6-2 having won 17 of the previous 18.

By the end of Saturday's game, Madrid were shattered. That team whose physical condition had us open-mouthed in awe, that Manolo Preciado described as "bestial", that appeared unstoppable, looked drained. And for all the mistakes they made, that was partly down to Barça. As one player puts it: "When you play Barcelona you chase the ball. You think you're going to get to it and they move it on, so you chase some more and you think you're going to get to it, and they move it on again, so you chase some more and so more and some more. And you're knackered … and you look up at the scoreboard and you think: 'shit, there are still 88 minutes of this left'."

That's not just because Barcelona move the ball but when they move it. Because – and this is a risk – they show it to you and take it away from you. Just look at Messi's role in the first and third, the way that players are sucked in towards him only to be taken out of the game with a pass. Or look at the way that Xavi and Iniesta – extraordinary in the second half on Saturday – play. Or Gerard Piqué and Dani Alves. Even Sergio Busquets appears to take risks until you realise that it can't be coincidence that he keeps getting away with it. And then there's Valdés, passing his way out of trouble even after he has passed his way into it. As well as talent, that takes balls. Especially against a team as good as Real Madrid.

The idea is clear. Is that the only way of playing good football? No. Is it morally better? No. But it works. So far, at least. It won't for ever, but for now their run is almost unbelievably good. "Effective" and "pragmatic" have become short-hand for direct and defensive, for the antithesis of what Barcelona do. But what can be more effective than Barcelona's record? Guardiola has been defined in many terms but rarely as, simply, "a winner". Yet under him, Barcelona have lost only one of 12 clásicos, the aggregate score against Mourinho's Madrid is 17-8, and Barça have won 12 trophies of 15. The three they lost? A Copa del Rey semi-final on away goals, a Copa del Rey final in extra time and a European Cup semi-final with a goal ruled out in the last minute. That reinforces the approach which, in turn, reinforces the success.

Valdés's mistake threatened to change everything but it changed nothing. On Saturday night, Barcelona did what Barcelona do. They won.

*Madrid would have been six points clear with a game in hand that everyone assumed (perhaps wrongly?) that they would win.

Talking points

• Any minute now, the Atlético Madrid president Enrique Cerezo will say there is no way that the coach Gregorio Manzano is going to get sacked and that we must be a bunch of nasty cynics for thinking such a thing. The idea, he will say, never even crossed his mind, despite their 4-2 defeat in Barcelona on Sunday night, and Manzano will be here to the end of the season. And how can you even think that? And how could you not trust us? And we're a serious club. Cerezo will say all of that and probably more. And when he does, Manzano will know that he's screwed.

• Racing Santander got a late draw against Athletic Bilbao on Sunday night. And although they were a bit lucky you couldn't say it was entirely undeserved either. Maybe that temporary triumvirate isn't such a bad idea after all. Next week they have a huge match – and it's not the one on the pitch. Instead, it is the assembly on 17th and 18th. Drama is guaranteed.

• In the 90th minute, Betis were 1-0 down against Valencia, in the relegation zone and their coach Pepe Mel was, in all likelihood, in the dole queue. Four minutes later, they had won 2-1 and climbed to 13th. Seven teams are separated by a single point from 18th to 12th and Betis are certainly not safe but they deserved to finally get the win – and the celebrations were a joy to behold, with Iriney hugging Mel and then leaping into the arms of a giant foam palm with a colossal grin on his face.

Results: Levante 1-0 Sevilla, Betis 2-1 Valencia, Real Madrid 1-3 Barcelona, Rayo 1-3 Sporting, Getafe 1-0 Getafe, Villarreal 1-1 Real Sociedad, Zaragoza 0-1 Mallorca, Málaga 1-1 Osasuna, Athletic 1-1 Racing Santander, Espanyol 4-2 Atlético.

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