Early strike from the Argentine, efforts by Dzeko and Silva and Pizarro's first City goal fire the Citizens into the next round of the competition as they eliminate the holders
Manchester City beat Porto 4-0 at the Etihad Stadium to wrap up a 6-1 aggregate win to set up a Europa League last-16 tie against either Legia Warsaw or Sporting Lisbon.
The home side took the lead after just 19 seconds through Sergio Aguero before the Argentine set up Edin Dzeko in the second half to secure a comfortable victory. David Silva and David Pizarro netted late on to give the tie a one-sided look.
Boss Roberto Mancini made just one change from the first leg, bringing in Aguero for Mario Balotelli, while the Europa League holders made two alterations to their back-line from the game at the Estadio Dragao as Nicolas Otamendi and Alex Sandro replaced Danilo and the suspended Alvaro Pereira.
Mancini had discussed Porto's threat before the game but saw his side make the perfect start to the match when Yaya Toure pounced on Otamendi’s slack pass to feed Aguero through on goal and slot home past Helton to score his 20th goal of a highly impressive debut season.
The home side almost extended their lead as a clever Silva pass sent Toure through on goal, only for the Ivorian to see his effort saved.
Moutinho hit a free kick over before Aguero again found himself with just the goalkeeper to beat. The Brazilian Helton recklessly rushed off his line to allow the Argentine to cooly round the keeper and chip an effort over Sandro on the line, only to see his effort cruelly clip the bar and stay out.
Porto were restricted to long-range efforts, Lucho Gonzalez hit a speculative effort over before a Hulk free kick was deflected wide.
From the resulting corner Maicon headed down to Otamendi but the defender could only volley over from eight yards. It turned out to be the Portuguese side's last chance of the half as the sides went in at the break with City in total control.
Needing three goals without reply, Porto came out for the second half with purpose. Lucho Gonzalez found space after a quick free kick and fired an effort wide with Hart scrambling to his right.
The holders finally had the ball in the net just before the hour mark, but James Rodriguez close-range goal was chalked off due to Hulk's involvement from an offside position.
Mancini looked to stem the tide of Porto pressure, sending on James Milner in place of Gareth Barry in the City midfield.
Toure picked up a booking mid-way through the second period for clumsy challenge on Fernando, meaning the Ivorian will now miss City's next Europa League game after picking up three yellow cards in Europe this season.
With the game meandering to little more than a training match, Dzeko replaced Nasri and immediately added a second to dash any fading Porto hopes.
Aguero combined with Silva on the left flank and drove inside before playing a perfectly weighted ball for Dzeko to finish.
In the aftermath, Porto's Rolando was shown a second yellow card and subsequent red for over-zealous protesting that the Bosnian had been offside.
Silva tapped in a third before late substitute David Pizarro pounced on a loose ball to smash the home for his first goal for the club since joining from Roma on loan.
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