The Premier League champions currently sit bottom of their group, labelled by many as this season's infamous 'group of death', after losing to both Real Madrid and Ajax and scraping a draw against Borussia Dortmund.
And with chances of qualification for the latter stages now looking extremely slim, the 47-year-old manager has confessed that he does not believe his side have what it takes to win Europe's premier competition yet.
"I don't think we're ready to win the Champions League," he told The Guardian.
|MISSED CHANCES WORRY MANCINI
|40/1||Manchester City are 40/1 with William Hill to win the Champions League
"We're a good team but we're not ready in the Champions League, like the other teams. Chelsea tried for 10 years to win the Champions League. They were probably the best team in Europe for 10 years and they won it [last May] after 10 years, probably when they didn't deserve to. They deserved to win it three or four years before."
Yet despite the seemingly impossible task faced by Mancini and his troops, the Italian still expects the players to go all out in order to collect nine points from the three remaining games.
"The players owe me three big performances," he added.
"We have less chance of qualifying for the next round but, when you're a top team, even when you're out, you should play 100% in every game.
"We have three games left but we are only focusing on Ajax. There's no mental problem [in the Champions League]. The players are the same and the referees are the same. We just need to improve. I will change nothing."