There is a feeling that City might be better served in their Premier League title defence by being out of Europe altogether now, but Mancini has disputed that.
The Italian also insists the upcoming derby has not clouded his thinking for the Dortmund game.
Mancini said: "We are a good team. We are a good club. We want to play well tomorrow and try to win.
"We have brought here all the players that are available. The other players that stay at home are injured.
"The players that are here will do everything to win this game.
"It will be difficult because I think in this moment Borussia are one of the best teams in Europe."