Samba's brace came in an unfamiliar position, with Brazilian winger Allan also among the scorers on his own debut, adding a goal and an assist to a lopsided scoreline at the Etihad.
Maresca revealed afterwards that he had thrown Samba into a role the youngster had never previously played.
"I'm satisfied not just for the two goals, but for the entire performance — he was good," Maresca said. "He didn't play many games as a No. 9, but we tried him there in the last few days.
"I asked him in the last three or four days when I decided to play him as a nine — I asked him if he had played that role and he said he had never played there before!"
Maresca praised the teenager's composure in an unfamiliar role, while cautioning against getting carried away.
"He's very good at finishing so I think it was a good game for him. He is not a 9 for sure but he was good, he is young, full of energy, he is strong, he can finish and he made some good decisions, some passes to team-mates," Maresca said. "So I am happy, but again, they are young and we need to go slowly with them."
The Manchester City boss pointed to a congested fixture list as the reason for patience with his younger players.
"We have different competitions. We have many games. We are just at the beginning of the season — for sure the ones that played tonight during the season will play Premier League games and Champions League games as the season is so long," he said. "I said we had Antoine there, depends a little, but the game plan we can use Phil and Rayan as a false nine, but for sure he played tonight, he was good and hopefully we can give him more chances."
Maresca was equally pleased with Allan's introduction to English football.
"It was a good performance. It was not easy — the first minutes here at home is always complicated," he said. "I think it was important for him to play, to see a little bit of the English competition is a bit different to South America, so overall, it was good — he scored a goal and an assist, I think he is happy!"