The Italian is under no allusions to the task at hand against their rivals on Sunday, and admits they needed a 'United mentality' to defeat Villarreal in midweek
City travel to Old Trafford topping the Premier League, two points clear of the reigning champions, and have only dropped two points in their current campaign with a 2-2 draw with Fulham.
The Italian is confident that his team can come away with at least a point on Sunday, despite United’s fantastic home record which has seen the Red Devils win 24 of their last 25 games at Old Trafford.
"We don't have any problems or pressure, we have 25 good players and no injuries," Mancini told reporters.
"The derby is usually different from other games but in this case it is very different, because for the first time in a long time we can go there on top.
"We know that it will be a very hard game because United at home are incredible. It's important that we are ready to play a good game and defend very well, because they have fantastic strikers.
"If we leave Old Trafford with a draw that is good for us, but that is not our mentality, and it's the same for United. Like us, they always want to win every game.
"If we win it will be important but I don't think it will change anything because the season is long. I'm happy that our supporters are happy, but to stay up there you have to work very hard."
City won in dramatic fashion on Tuesday in their Champions League game against Villarreal, with Sergio Aguero snatching the winning goal in the dying seconds of the game.
Mancini feels his team displayed characteristics similar to those of United, adding: "When we score in the last minute that is perfect! If we had drawn it would have made things very difficult. I was happy for Sergio that he scored.
"United have this mentality, they are still trying to win in the last second. We wanted to win and tried right to the end. Milner and Zabaleta were fantastic for that goal."