The game at the Etihad Stadium follows Tuesday’s 1-0 defeat at Borussia Dortmund, the final chapter of City’s torrid Champions League campaign.
Nonetheless, the reigning Premier League champions have not let their poor form in Europe affect their domestic campaign.
A win in the derby would see them leapfrog United into first place, and Mancini is confident his players can bounce back from their midweek disappointment.
Mancini told Sky Sports: “I don’t think there will be a problem with morale.
“It is important that we only think about the derby. We have five days to recover our strength, and then I don’t think there will be a problem.”
The loss to Dortmund left Mancini’s men winless in six group matches, as they also failed to finish third and qualify for the round of 32 in the Europa League. However Mancini acknowledged this would help them in trying to retain the title.
He said: “It could be a good thing because we won’t be playing on Thursdays.
“But we are playing against a team like United, that is used to playing every week in the Champions league and the Premier League. It depends on us now, I think.”
City may have to do without their star midfielder David Silva for the top-of-the-table showdown against United. The Spaniard didn’t travel with the team to Dortmund this week due to a hamstring injury.