The Eastlands outfit came from a goal down to secure a key advantage heading into next week's second leg, with the Italian suggesting his side thoroughly deserved the win
City went behind in the first half after a Silvestre Varela strike, but an own goal from Alvaro Pereira and a Sergio Aguero strike late on handed the visitors the advantage ahead of next week's second leg back in Manchester.
"I think that we played a good game," Mancini told ITV Sport. "We played very well. Also in the first half we had three or four chances to score. We were really unlucky, but in the second half we played very well.
"Second half maybe we stayed higher and played better, but we had seven or eight chances to score in this game. We didn't leave any chances to Porto. I think this is important because Porto is a top team."
Mario Balotelli played an integral part in City's equaliser, and was also allegedly racially abused by some sections of the home crowd. However, Mancini insists that he did not hear said abuse.
"I didn't hear any, sorry. I didn't hear," he insisted.