Mancini raised eyebrows on Friday when he claimed Carlo Ancelotti's side were the best in England and would retain their title "easily".
Yet even after Carlos Tevez had scored an excellent second-half winner to give City their third straight win against Chelsea after completing the double last term, Mancini did not change his view.
"I still think they will win it easily because I think they are the best team in the Premier League," he said.
"It is not possible for them to score five goals every game."
He continued: "Sometimes you might get a result like today. But they are the better team.
"I hope the result will be important for us," he said. "But we cannot think everything is OK just because we won this game."
Chelsea boss Carlo Ancelotti admitted Manchester City's midfield strength caused his side's first Barclays Premier League defeat of the season.
"We wanted to play better. As a team we didn't play well. We saw the power of Manchester City in midfield. We lost a lot of tackles and we were not able to play our football in the opponents' half.
"We played too complicated and gave the opportunity to them to take the ball and go on the counter-attack.
"We are disappointed but we have to look forward. We are still top of the table. It was an important game, but every game is important. We did well five times then this time we lost.
"It is difficult to judge this team by one defeat. Our moment is very good, we are doing very well. It was not a good day but this team has a very good mentality."
Source: PA
Source: PA