Erling Haaland's second-half brace settled a tense opening Champions League fixture at Estádio do Dragão, extending Manchester City's winning start under Maresca to four from four across all competitions.
Diogo Costa denied City repeatedly in a goalless first half before Haaland struck twice after the break to see off the Portuguese champions, with 18-year-old debutant Ayyoub Bouaddi impressing at the base of midfield throughout.
"It was the complete performance on the ball and off the ball for 95 minutes," Maresca said. "We created enough chances to win the game in the first half and their goalkeeper was very good. We tried to continue in the second half in the same way. It's game by game.
"It's a different competition, different stadium, but the most important thing is we show who we are. We try to be aggressive off the ball and on the ball, try to plan how we can win the game.
"In terms of where we are, I don't know. I can see game after game, the team is improving."
Maresca was pleased with how his young midfielder handled the physicality of the occasion, with Porto claiming Marc Guéhi should have seen red for an accidental elbow on Gabriel Veiga during a fiery contest.
"From Erling, Rúben [Dias], Mateo [Kovačić] you expect how to manage this game, but he was never in panic, Ayyoub Bouaddi. He was very good, and I think the performance was unbelievable," Maresca said. "I think we could've scored more goals, especially in the first half, but overall I think we deserved to win the game. We created enough chances to win the game. We didn't concede a lot.
"It's normal to come here and concede some chances because it's normal, so overall happy with the performance. I think I am lucky because all the squad is good players — for a manager it is easy because you can give minutes to all of them, and tonight I think the guys that were inside were very good."
On negotiating the game's more combative moments, Maresca credited his side's composure.
"Very pleased. We know in these games, when you come here it's difficult. That's the way they grow up, but it's normal. We dealt with it very good," he said. "I watch games from the Portuguese league, especially now with Porto and Sporting. I watch different games and you can see the level is very high. Porto play very good, Francesco [Farioli] is doing a fantastic job, but we managed it and won the game."