City finished bottom of their group without a win in six games, signing off with a 1-0 defeat at Borussia Dortmund on Tuesday to exit the competition with the worst record of any English side.
Attention now turns to domestic affairs, with the Manchester derby on Sunday at the Etihad Stadium, and Mancini is adamant that their campaign is far from over.
"It's clear the season isn't finished. We have the Premier League and FA Cup to go for," he told reporters, "but we must work more now. What we're doing is not enough.
"Our target when we started the season was to defend our title. That was the main target.
|5/6||Manchester City are 5/6 with PaddyPower to lose out to Manchester United for the Premier League title|
"We knew it was difficult to win the Champions League but our target in Europe was to get into the second stage.
"We wanted to get to the Champions League second stage - then in February, when you're there, you can change your target. But we didn't and now we can't.
"I don't feel any pressure. I'm disappointed because we went out of the Champions League and I'm disappointed for the club because they deserve to go through and for our players, who deserve to play on that stage."