The Italian manager was disappointed with his side's performance in the dour 0-0 draw at Stamford Bridge on Sunday, following their midweek Champions League elimination
Having lost their place at the top of the table to rivals Manchester United on Saturday, the defending champions failed to return to the summit after playing out a disappointing 0-0 draw against the European title holders, who were playing for the first time under interim boss Rafa Benitez.
"It's two points dropped," Mancini told Sky Sports. "It's difficult to play here. Last year we played very well in the first half and scored one goal, but then we lost.
"Here, we dominated the game but we were missing in the last 25 or 30 metres [of the pitch], we were poor. That's the problem.
"We dominated the first half. In the second half, maybe Chelsea did better. It is not easy to play against Chelsea like we did, but we need to be strong when we get to the edge of the box, not soft. We were too soft.
"When we are near the box we should be very strong. Today we played very well until the edge of the box, where we were poor."
Mancini chose to start with Edin Dzeko after the Bosnian scored five goals from the bench this season, but the striker - along with Sergio Aguero, and substitutes Carlos Tevez and Mario Balotelli - failed to fire.
"I hoped that [Dzeko] would play well from the start like he does when he is a substitute. Today, I think every player gave 100 per cent but sometimes it is not possible to play well."
However, the Italian was also keen to highlight the better parts of the performance by his side, who remain unbeaten in the Premier League so far this season.
"There are positives," Mancini continued. "We didn't lose, we played well after the Real Madrid game, our attitude was good.
"The only thing that was missing was the last pass for the striker. The strikers should be very strong around the box.
"I think that we played very well, but we were missing a goal. We had a lot of chances and got to their box but we were missing the last pass. But other than that, I think we played well."