City managed to claw back an eight-point deficit to win their first top-flight title since 1968 last season.
And the City boss is still convinced that his side have what it takes to pip United to the trophy again.
He said: “If we could do it like last year when we were eight points behind with six games to go, it’s not impossible that we can recover with 14 games left.
“We could recover five or six points and still lose, but we’ll do everything to win this championship.”
“[Beating Madrid] would be another two games for them. I will go there and support them with a red and white flag,” Mancini added.
“But playing Real is tough, they are one of the best in the world. Them and Barcelona.”
Betfair are offering new customers enhanced odds of 6/1 on Chelsea or 10/1 on Man United to win Sunday's game. Click here to sign up now.
MORE: The latest football news