City have collected just one point from their opening two games in Group A of the competition after a 1-1 home draw with Napoli was followed by a 2-0 loss at Bayern Munich.
The manner of that defeat, in which City struggled to force their way back into contention after falling behind, has been overshadowed by the controversy surrounding Carlos Tevez's non-appearance as a substitute.
Yet until Bayern struck twice late in the first half, Mancini was pleased with the performance of his side and feels that will stand them in good stead as the action resumes this week.
City face Villarreal at the Etihad Stadium needing a positive result to keep themselves firmly in the battle for a top-two spot in the group.
Mancini said: "I think the only problem we had in Munich was the result.
"For 50 minutes we played very well and should have had two penalties.
"Their second goal in the last second (of the first half) closed the game.
"After the game it is easy (to say) but for 50 minutes we played fantastic football against Munich in Munich."
The defeat will also be remembered for the angry reaction of striker Edin Dzeko when substituted.
Mancini's decision to replace Dzeko with midfielder Nigel de Jong attracted some criticism but while the Italian does not necessarily believe that was a mistake, he feels he is always learning from experience.
Mancini said: "Every manager, when they decide their first XI or make one change, think they have made a good choice.
"After if you think you could have done this or made one change, this is normal for a manager.
"You always think there are ways you could do better.
"When you lose or, for me, when I win I think if I could have made a change, this is my job.
"Like other men, we can make mistakes sometimes."
Another factor in the loss a fortnight ago, Mancini believes, was possibly fatigue.
But with the Villarreal game coming between Premier League games against Aston Villa and arch rivals Manchester United, it is something the club have to get used to.
Mancini added: "Some players were maybe tired because we played many games in a row.
"But we now play every three days for one month until the next international break."