Barcelona defeated 10 men Manchester City in an intriguing game at the Etihad, which leaves the Blues with much work to do in the second leg at the Nou Camp.
Messi put the Catalan side up from the spot early in the second half after Demichelis brought down the Argentinean just on the edge of the penalty area, before Demichelis got himself sent off and then Dani Alvez doubled their lead late in the second half to all but end City's European dream.
After such a massive build up for one of the most anticipated Champions League games of the year, Barcelona dominated the early stages of the encounter in their conventional tradition.
Yet in their domination, City applied their attacking mentality on the break, and easily made the better chances in the first half with Negredo proving wasteful on an evening where City must've taken their chances.
Xavi had Barcelona's only meaningful chance of the first half after stinging Joe Hart's hands from long range on half an hour, however the Catalan side couldn't turn their significant possession into many chance.
Pellegrini said his side won't change their approach for the visit of Barcelona, and he stuck to his word, as City broke with their flowing football.
Toure was a great asset when City were attacking, gliding through half-hearted tackles, connecting their defensive to attack.
With Silva dropping into a 5 man midfield to try and combat Barcelona's dominative midfield, one must wonder how City would've fared if Pellegrini would've played Garcia in a defensive midfield role while putting Toure ahead of him and Fernandinho.
This would've helped City hold the ball and would've given them much more of a central presence in midfield instead of losing the ball rashly attempting to get the ball up to Silva against Pique.
However Silva's incisive pass such as his fantastic pass on the 20 minute mark for Negredo, could've just nudged Pellegrini's decision.
Again, City had their parts of attacking football in the second half, but the inevitability of Demichelis getting caught out by the pace and sheer brilliance of Messi finally arrived.
After encouraging work and his tight defensive play, Demichelis became too tight on Messi, and let the Argentinean wizard finally get the better of him, breaking away from him during the 52nd minute.
The defender slide tackled him with no chance of getting the ball, and as last man, Demichelis made his side's task much, much harder with 40 minutes to go.
That was even before Messi cooly slid in the penalty in the middle of the goal as Joe Hart hopelessly saw the ball drift in the net. Neymar's introduction with 20 minutes to go wasn't a particularly attractive sight, after seeing City run around for the 20 minutes before that.
Demichelis may have got a few dirty looks for that in the changing room after the match.
City's attacking football was a good plus to go into the Nou Camp, after a good chance for David Silva, on a crisp right foot volley made Valdez make a save low to his right side.
With City showing encouraging signs going forward, they showed their naivety to keep it at 1-0 as Dani Alvez played a neat one-two with Neymar before slotting through the legs of Hart which rounded off a miserable and rather disappointing night for Manchester City.
It'll be disheartening for the players and it'll sting them on the way back to their homes that they couldn't take their chances on a night where it was imperative they either stopped Barcelona from scoring, or they took a lead into the Nou Camp.
Neither happened, and City find themselves facing an uphill battle in the second leg.
Dani Alvez: 8
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