Xavi's fortunate second strike turned the game around for Barca.
First, what a game.
La Liga is often described as a slow, luxurious league of leisurely, technical football. Tonight was anything but in terms of speed and intensity, even for a Barca-Madrid derby.
Rather than turning that fire into confrontation, fisticuffs and unsightly physicality, tonight's game was a back-and-forth spectacle of furious attacking football from both sides. Real only needed to draw, but they tried to play a positive game, even if it was restrained by a conservative lockdown approach to protecting their lines, at least in the first half.
Barca started nervy but thanks to the quality of their match-winning individuals they managed to ride out their panic and stress to take all three points: a huge result for the Catalans who can now take control of the La Liga campaign and find new confidence in their approach and abilities.
Here are five points on how tonight's El Clasico was won, and lost, by Barca and Real respectively.
Messi was all over the pitch, winning balls and driving his team on.
The run was excellent, the assisting through ball even better, but it was Messi's determination and energy that turned the game for Barca.
Tonight he was everywhere; closing down deep within his own half, pacing forward to open up space for others, battling down with Madrid's enforcers in the middle; he was their bright spark in a drab first half.
With Barca's nerves getting the better of them, Messi stepped up and dragged his team to their feet, shoving the initiative back into their hands.
Another exceptional El Clasico performance by the world's best player.
Ronaldo may be brilliant as an individual but he just isn't effective within the context of a team.
Whilst his Argentine nemesis powered his team back on track towards glory, Cristiano Ronaldo went missing.
Ineffectual whilst Madrid held the upper hand, he later looked isolated when Barcelona finally took control of the fixture. Whereas Messi dug deep and wrestled the game back into the hands of Barcelona, Ronaldo drifted more and more into his tunnel-visioned egotism, trying to score with every touch and taking the ball on himself regardless of the options around him.
Messi is brilliant because he can integrate his individual genius within Barca's communal system of fluid, attacking football. At times last season especially, Madrid seemed set up to feed Ronaldo and his hunger for individual records and rewards.
To this end, Ronaldo, undoubtably an exceptional individual, is a destructively selfish footballer in the modern game. He asks what his team can do for him rather than trying all he can to sacrifice himself for the cause when they need him most.
A disappointing display from Portugal's premier player, but a knowing confirmation of his inferiority when placed alongside Lionel Messi.
Sanchez put the finish onto Messi's first half through ball.
Throughout the first half, Mourinho's plan of playing a midfield combination of tackler-passer-creator with Diarra, Alonso and Ozil seemed to work for Madrid. Whilst they were perhaps still a man short, support from Coentrao cutting in from the right helped Mou's men dominate the area in front of their box.
Coupled with Barca's stage fright, Madrid bossed the middle of the park, leaving Barcelona to rely on their speed and trickery on the flanks to try and break down their great rivals. Messi, Sanchez, Fabregas and Iniesta all drifted, switched and roamed out wide and back in trying to find inroads but were ultimately unsuccessful, as was the efficiency of Mourinho's plan to lock down and hold steady after their early one-goal lead.
After Sanchez's opener however, supplied of course by Lionel Messi, the game changed. As Barcelona grew more confident, Madrid changed their focus, needing to be both wary of further pressure from their refocused opponents and wise to options going forward to reassert their lead.
This inevitably broke up their shape to some extent, allowing more space for Barca's clever short passing game and movement that lead to Xavi's lucky second goal that took a harsh deflection off Marcelo.
With a second goal, Barca's heads were truly back up and they snapped back into their usual rhythm as Madrid's confidence plunged.
Andres Iniesta was Barcelona's key man in the second half.
Whilst Messi was Barca's fire-starter in the first half, it was Iniesta who overcame his marker, Fabio Coentrao, to guide and shape his side's resurgence in the second.
Running into the space on Madrid's right flank, Iniesta undermined Mourinho's tactical trickery and vault building to crack open the defensive safe of the back four. His dribbles and surges were incisive and ever-threatening, crafting chance after chance for his teammates, even if they struggled to make the most out of them.
He too, like Messi, was committed to running down his opponent and their passing work. Not only a threat in defence, he picked apart Madrid's patterns whenever he could.
Andres Iniesta has become football's ultimate big-game player over the last few years and tonight, he was Barcelona's man of the match.
Mou saw his plans shattered by individual genius and the reawakening of Catalan's giants.
Jose Mourinho, after last year's spoiler tactics and cynicism, tried to succeed in tonight's Clasico with attacking football that, whilst not completely clean and honest by either side, was eye-catching all the same.
The contest was ferocious yet still sporting for the most part—no 50-man street fights on the pitch tonight! At times it seemed almost super-charged and sped up compared to most La Liga contests, almost like a technically excellent English FA cup final or North West derby, with Spanish flair and fantasy in place of blunted blood and thunder.
It wasn't a truly purist match. The football was excellent but not spotless. Mistakes are made when the game is played with such vigour, however, regardless of the expertise of the combatants.
Tonight, Mourinho may well lie back in his chair, a glass of wine in his hand, and splutter a laugh of indignation. He can't beat Pep's Barca with underhand tactics, cynical brutality or solid excellence. What does the special one have to do to look special against perhaps his greatest-ever foe?: FC Barcelona.