Manchester City came from behind to beat Porto 2-1 in the first leg of their Europa League knockout tie in Portugal.
Joao Moutinho dragged his shot wide after 17 minutes for the hosts before Samir Nasri had his effort pushed away by Helton.
Porto went ahead on 27 minutes when Silvestre Varela met Hulk's cross to power in from six yards.
Mario Balotelli nearly drew the visitors level instantly, but the Italian's half-volley was saved.
Hulk had a good opportunity to double his side's lead just before half time, but the Brazilian could only blaze his shot over.
City started strongly after the interval and were rewarded on 55 minutes when Alvaro Pereira knocked the ball past his keeper with his shoulder from Yaya Toure's searching cross.
Both sides found it difficult to create chances for the remainder of the half, but City found a winner with five minutes to play when substitute Sergio Aguero tapped in after being put through by Yaya Toure.
