He says he can see signs of Manchester United tiring while City are getting stronger and he wants the gap cut over the next two games before the derby on Monday April 8.
Mancini said: "When you play every three days and it's always a top game, you're tired. We're getting stronger.
"We need to win every match from now.
"The next two or three matches are crucial. If they can lose points in the next two games then we've the derby. We want the gap cut to nine or seven points by then."