Mancini blamed himself for the loss in the game's immediate aftermath, but that said was down to his preparations and not his tactical changes during the second half.
The Italian said: "If you have spirit you have quality to play Champions League. If not, you can't. This is the problem. It is not important, the tactics. When you play this game you should have good spirit.
"We are a young club for the Champions League. This is the second time that we play. I think we need to work more for the Champions League."