City have conceded an alarming number of goals in such a manner this season, and did so again against Tottenham on Sunday before fighting back to claim a 2-1 win.
Some of the blame has been pinned on the zonal marking system which details players to take charge of areas, rather than players.
Mancini does not believe it is a problem. In fact, the City boss thinks it would be worse if he tried it the other way.
"We are not strong enough to mark man-to-man, and every time we do there is a risk of conceding a penalty," said Mancini.
"If we work, we can improve the system. We have let in goals because of it, but we can change that. We are working on it, but we need to work more."