Roberto Mancini was left to rue a missed opportunity after the Blues surrendered their unbeaten record but not top spot at Stamford Bridge.
The City manager had no argument with Gael Clichy's sending off early in the second half but did take issue with referee Mark Clattenburg’s decision not to award a first half penalty when a David Silva looked to have been brought down by Boswinga.
“We should have scored two or three goals in the first half and when you don’t take your chances you can lose a game like this,” lamented Mancini.
“We played fantastic at times. Gael Clichy probably deserved the yellow cards but that was not the turning point.
“The turning point was when we did not get a penalty in the first half. The referee was only a few metres away and was not certain but he was certain when the ball struck Joleon Lescott’s arm from just a few metres away in the second half.
I think we should have had a penalty
Mancini now hopes his side is able to go on a repeat of the fourteen game unbeaten run that took the Blues clear at the summit of the a Premier League.
“We can do nothing about this result now; it is gone,” he went on. “We are still top of the table and we are strong enough to recover. We know that this is a long season and that many teams still have a chance to challenge.
“Chelsea were really happy to beat us. You could see that at the end of the game. This shows me we are a top team. We must now carry on like we have been doing - starting with Arsenal on Sunday.”
Andre Villa-Boas felt his side deserved to be the first to beat City in domestic competition this season.
“It was always going to be a game decided by small detail,” he said. “My players did brilliantly.
“They felt the game and adapted to well to it. It was a tremendous game from both teams.”