Porto: Sergio Aguero came off the bench to score a late tap-in that handed Manchester City a 2-1 win over holders Porto and put them in the driving seat to reach the Europa League last 16 on Thursday.   

Porto had controlled the first half at the Dragao Stadium, scoring the opener through Portugal international Silvestre Varela in the 27th minute.   

But the hosts lost their way following the interval and allowed City to draw level thanks to an own goal by Uruguay international Alvaro Pereira before Aguero's effort handed them a comfortable cushion ahead of next week's second leg in Manchester.   

Porto and City both dropped into the second-tier Europa League after group-stage exits from the Champions League.   

"That mistake (own goal) was fatal because from then onwards we became more exposed," said Porto coach Vitor Pereira.   

"We came face to face with a team that was extremely strong in physical terms."   

Porto goalkeeper Helton was kept busy midway through the first half as he pulled off three saves in quick succession, frustrating Mario Balotelli, Micah Richards and France midfielder Samir Nasri.   

The hosts broke the deadlock when pacy Portugal winger Varela pounced on a low cross from burly Brazilian Hulk before tapping in the opener which sent the home crowd into a frenzy.    

However, Ivory Coast midfielder Yaya Toure, back in club action after his national side lost the African Nations Cup final to Zambia on Sunday, was a powerhouse during the second half.   

His long range effort left Pereira and Balotelli tussling for the ball and the Uruguayan defender could only watch on in horror as he accidentally    diverted the ball into his own net.   

Toure went on to sprint into Porto's box with five minutes to go and set up substitute Aguero for the dramatic winner.