City's dismal campaign in Europe's elite competition came to an underwhelming conclusion with a 1-0 defeat at Borussia Dortmund. It left them bottom of Group D with just three points - the worst return by an English side in Champions League history - and without even the consolation of a place in the Europa League.
Mancini said: "I think that we had a difficult group. It was (also difficult) last year but we had also a good team. We had a good team and we got only three points - this is not good for us."
The Italian added: "We are disappointed we didn't go into the second stage of the Champions League and we are also disappointed because we didn't stay in the Europa League.
"But it is clear the season is not finished. We have the Premier League and the FA Cup. I think that we need to work more now to improve this problem we have with the goals (scoring). What we continued to do is not enough. We need to work more."
Mancini has bemoaned the lack of goal output from his principal strikers in recent weeks and was again frustrated as they failed to find in the net at the Westfalenstadion. Ath the other end, Joe Hart saved well from Ivan Perisic and Kevin Grosskreutz but Julian Schieber turned in a Jakub Blaszczykowski cross for the only goal in the 57th minute.
With Ajax losing to Real Madrid, the opportunity had been there for City to seize third place in the group but they were unable to get back into the game. The players were reluctant to speak about their disappointment afterwards.
But Scott Sinclair, who has struggled to make an impression at City since his August move from Swansea and who made his first start since September against the German side, did speak to City TV about the Premier League champions' regrets.
The 23-year-old said: "It is a disappointment but now we have got to move on and concentrate on the Premier League. All the players have a winning mentality and every game we want to win.
"It was a tough group but I am sure when it comes round again everyone will be more aware of it and make sure we do better."
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