Barcelona dominated possession with wonderful passing, working tirelessly to harass the home side in their short spells on the ball, and deservedly led through a David Villa goal after 26 minutes.
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They could have had three or four more but Arsenal levelled out of the blue through Robin van Persie in the 78th minute.
That would have been kind on Arsenal, beaten 6-3 on aggregate by the Spaniards in last season's quarter-finals, but they got a huge bonus seven minutes from time when substitute Andrei Arshavin swept in the second after a superb counter-attack.
"They are the best side in football's history in my opinion. That is one game and this is half-time," Arsenal captain Cesc Fabregas told ITV Sport.
"It is a nice victory but that's all. If we show it here and not the Camp Nou, it is nothing for us."
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Dutchman Van Persie, who missed both matches in last year's quarter-final, said Arsenal had beaten Barcelona at their own game.
"In our opinion if you drop back too much they are so good they will beat you," he said. "We had to beat them in their own style. It was a fantastic result in the end."
Arsenal actually started well and it needed a good save by Victor Valdes to block a Van Persie shot after five minutes following a clever flick by Fabregas.
But it was a false dawn as the visitors quickly settled into their well-worn rhythm, moving Arsenal this way and that before slicing them open repeatedly with practically identical passes between the centre-backs.
DINKED FINISH
Messi ran on to the first from Villa after 15 minutes but though the striker's dummy took Arsenal keeper Wojciech Szczesny out of the equation his dinked finish rolled inches wide.
The goal came when Messi returned the compliment and Villa, in acres of space, tucked the ball away with the minimum of fuss.
It could have been more as Arsenal were chasing shadows with the Spaniards enjoying 61 percent of possession in the first half and completing more than twice as many passes as their hosts during the match.
When Arsenal did begin to get some of the ball after the break Barca gave them another lesson, this time in the art of closing down, as they showed that like all great teams they know how to work hard and defend when they have to.
The game seemed to be heading only one way until the ball broke to Van Persie wide on the left with little apparent
