Goals from Rodrigo Palacio, Mauro Icardi and Nemanja Vidic led Inter to a 3-1 victory over Genoa on Sunday, although Mancini thinks his side could have done more to assert their dominance, particularly in the second half.
The hosts, having led at the break, allowed Genoa back into the game and looked set for a nervous final five minutes as Armando Izzo pulled a goal back, only for Vidic to seal the win.
Mancini opted to deploy three attacking players – including Lukas Podolski – in support of Icardi for the match and, while he was happy with the three points, he expects more as his players become accustomed to the formation.
"I'm pleased with the result and the first half, not the second," he said. "But we had a lot of attacking players on the pitch and we struggled because a number of players aren't fully fit.
"Our aim was to press Genoa high but in the second half, once we started to fade, we no longer managed to cause them problems and get high up the pitch.
"The lads are working well but a win changes nothing. We need time and that's only natural.
"It was important to get a victory and perform well with this system. If we reach the right fitness levels and improve, we can play this formation."
Mancini's side move two points behind Genoa following the win and are four games unbeaten in the league.
