After a 1-1 draw with Real Madrid at the Etihad Stadium left his struggling team with only three points and winless in Group D ahead of next month's final group tie at Borussia Dortmund, the Italian said it would be "crazy" to believe the competition could be won after only two campaigns.
"The season is long, you have Champions League, the FA Cup, Premier League," he said. "If we think we can win the Champions League after only two years we are crazy. We need to improve as a team, we did some mistakes. We are a good team. I don't have fear for this.
"Inside [City] everyone knows football, and for us this is the second time [we've gone out at the group stage]. To win it first you need to go into the second stage. After February everything can change."
Asked what a reasonable amount of time would be for City's expensively assembled team to be considered contenders, he said: "Chelsea tried to win it for 10 years and in their best moment they didn't win – when they played with [Didier] Drogba when he was younger. They won last year when no one probably thought they could. The Champions League is strange. We need to be patient, we need to improve, also improve our team."
However, José Mourinho, whose Real Madrid side qualified in second place, suggested the patience afforded Mancini by City would not have been given to him had he failed in a similar manner. "That's good," he said. "A club must support their manager with the maximum they can, until the last day when they decide to make a change, a new life. But until the last day I admire the fact that clubs support managers.
"City are out of the Champions League but they are out with two big teams. Real Madrid and [Borussia] Dortmund [who won the group] are two very good teams and we knew from the beginning that a big team would be out. It's good that it was City because Roberto can work without any kind of problems, I believe. Because if it was Real Madrid the press wouldn't let me return to Madrid."
Mancini set out with a 3-5-2 formation that he discarded inside the opening half hour after Karim Benzema had opened the scoring for the visitors on 10 minutes. City were overwhelmed. The quick reversion to Mancini's normal 4-2-3-1 suggested a telling indecision, but the manager defended the switch. "We changed because we conceded a lot of space to them in the counterattack," he said. "If you don't have a good attitude at some moments you need to change things. We conceded a goal because we had two in the box to their five, not because we had three in defence.
"I thought before the game with three and [Aleksandar] Kolarov and Maicon down the channel it could be good for us, but then we left a lot of space in the counterattack [for them]."
Sergio Agüero won a 73rd-minute penalty that the striker converted to make it 1-1, but it was an unsettling night, capped by the sight of Vincent Kompany leaving the Etihad on crutches after the match. Mancini conceded the campaign has been a poor one. "This Champions League is worse than last season," he said. "We had only three points after five games, we made some mistakes, and this group was very difficult. We started this group with defeat in Madrid [3-2] when we were 2-1 up with four minutes to go and everything was complicated after that. But Madrid and Dortmund deserve to go through because they were better than us."
A place in the Europe League is not yet guaranteed, but Mancini said he would not regard a berth in that competition as a distraction from retaining the championship. "We will try to get into the Europa League. It may not be as big as the Champions League but if you arrive in the semi-final or final it could be an important trophy for us."
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