With both sides of Manchester challenging for the title for the first time in many years, the meeting has taken on added significance with Mancini saying there is little between them apart from a confidence that comes with trophies.
"Maybe United has more than us a winning mentality because they (have) won (for) a long time, I think this is the difference," the City boss, seeking to bring the club their first league title since 1968 and first silverware since the 1976 League Cup, told a news conference on Friday.
"I think that when we start to win trophies it can change. But when you are a team that wins for 20 years your mentality is very strong - when you don't play well you know that you are a strong team and if you don't concede a goal you can win.
"I think we are improving in this... I think that for us it is very important to win something at the end of the season - Europa League, FA Cup (or) Premier League."
United are seeking a record 19th league title and are moving towards it with a four-point lead over second-placed Arsenal at the top of the table. City are five points behind their city neighbours having played one game more.
City could be boosted by the return of striker Mario Balotelli, although he is pushing for a place on the bench rather than in the starting lineup after missing a month with a knee injury.
"I will decide if he can go on the bench. If he is not fit, maybe he will need another week," Mancini said.
Dutch midfielder Nigel de Jong is a doubt with an ankle injury after also missing last weekend's 3-0 victory over West Bromwich Albion and a midweek international friendly.
