First loss for Blues as Citizens close gap at top of the league...Chelsea's perfect league start was halted inside Eastlands as they were beaten 1-0 by Manchester City thanks to an excellent Carlos Tevez strike.
It is the third time in four games the Argentine has struck against the Blues and his strike from a good City break in the second half was enough to settle a tight encounter and ensured Carlo Ancelotti's men drop points for the first time in the league this season.
City's extensive injury list meant Mancini turned to 19-year-old Dedryck Boyata to plug the gap at right-back. David Silva was again prefered to Adam Johnson on the wing with Carlos Tevez once again fulfilling his familiar lone-striker role.
After Chelsea's humbling exit in the Carling Cup in midweek there were returns for most of the Blues' big guns. Didier Drogba, Florent Malouda and John Terry all started. Frank Lampard's continuing hernia problem meant there was also a place for Ramires in midfield.
As expected the start to the match was a cagey affair with both sides respectful of the danger the other team poses. But the first chance arrived when Chelsea were holding a particularly high-line on the field and this allowed Nigel de Jong to release Tevez through the back but the Argentinian could only drag his shot wide.
And City applied more pressure through the flanks courtesy of James Milner whose burst down the left was halted unfairly by Branislav Ivanovic. From the resultant free-kick, Milner crossed in right-footed but he put too much zip on it and the ball just evaded his waiting teammates in the box.
It appeared that both sides were cancelling each other out with Chelsea struggling to create anything in front of goal and City only producing half chances. The best the Blues had to show so far was a wild Nicolas Anelka blast from the edge of the box after the Frenchman had cut in onto his better foot.
The game did start to open up slightly after the half-hour mark was passed. Chelsea produced the best chance of the game so far when they were awarded a corner. Cole cut the ball back short to Malouda who shimmied onto the edge of the box and crossed to the far post. Anelka headed down to Ivanovic who hit the post with a shot and the Serb got a second chance as the rebound fell to him but Hart was well placed to save his follow-up effort.
City hit back minutes later with a good chance of their own. The increasingly busy Milner was picked out on the left by De Jong and the England international drilled an excellent pass to Tevez in front of goal, but the Argentine was relieved instantly of the ball in a dangerous area by an excellent Terry tackle.
And that was the tale of a first half where two well-drilled defensive systems were firmly on top of proceedings and goalscoring chances at an premium.
Midfield Terrier | De Jong's work in midfield halted the Chelsea engine
Neither side made any changes at the break but Chelsea were fast out the blocks with two decent chances within five minutes.
The first arrived after a good passing triangle by the Blues saw the ball worked up to Drogba in the final third. The Ivorian, who had struggled to make an impact all game, back-heeled into the path of Anelka who hit a powerful drive that whistled just wide and had Joe Hart diving dramatically to his left post.
Next, Chelsea were awarded a corner and they perhaps should have scored this time. For once the City defence were out of position and this allowed Essien to rise unchecked and head an effort whiskers over the bar from Drogba's corner.
The game was threatening to open up a little again as soon later City had a shot on target repelled. Some neat passing between De Jong, Milner and Silva culminated in the Spaniard driving into the box and the former Valencia star hit a vicious drive at an angle to goal to test Petr Cech at his near post.
Then the game certainly did open up when Chelsea went behind for the first time in the league on the 57th minute.
The Blues were caught on the break after a Drogba corner was defended and fell to Gareth Barry. The Englishman spotted Tevez breaking up the field and Argentinian was released with Silva galloping up the field next to him. The Spaniards presence served to split the Chelsea back-line and Tevez ran into the box and fired an accurate shot across goal to finally break the deadlock inside Eastlands.
It was a quality finish, but Ancelotti's men wouldn't be reigning champions if they shrunk after going behind and the Blues tried to hit back instantly.
Drogba was released over the top by a great Anelka dink and the Ivorian tried to do a Tevez, but he was crowded out and pushed wide by Kompany and his eventual shot was saved comfortably by Hart.
With Chelsea streaming forward more anxious to find a goal, City were now finding it easier to move the ball up into the final third. Yaya Toure profitted well from this when he went on a jinking run into the box, evading three defenders before the ball got stuck between his legs and the Blues defence was let off.
The Blues were not right and that was no better illustrated than when an ineffective Drogba was brought off and replaced by Daniel Sturridge. But the Londoners coudln't find a way through and this lead to a number of ambitious shots from range. Essien showed his frustration with a hopeful long range drive before Cole, with no options in the box, had a similarly ambitious shot at an angle that failed to threaten Hart in goal.
As the game wound to a close an increasingly desperate Chelsea threw men forward but Kompany and his defensive partners were keeping the champions shackled. Essien had the last shot on target for the Blues but again it was an effort from range which Hart dealt with comfortably.
City in fact had the last chance of the game when Adebayor charged into the box on the break but Cole did just enough to relieve him of the ball. But City won't mind as they beat Chelsea for the third time in a row and hand Ancelotti his first league defeat of the season.