The champion's dominant display was rewarded with second-half goals of real quality from Yaya Toure and substitute Carlos Tevez.
Toure’s 63rd-minute opener came shortly after Joe Hart had atoned for clumsily conceding a penalty by launching himself to his right to keep out Frank Lampard’s spot kick.
Tevez sealed the win five minutes from time to help City pull clear of Chelsea in second place and reduce Manchester United’s lead at the top back to 12 points.
Such is the dominance of the runaway leaders that the main fight is for the minor places but City demonstrated that it is not a completely diminished force by overwhelming its main rival for the runner-up spot.
City has fallen short in the goalscoring department this season and the solution of Mancini, who had criticized a number of his players in an interview earlier in the week, was to support spearhead Sergio Aguero with David Silva and a battery of midfielders. Yaya Toure, James Milner and Javi Garcia were supplemented by Jack Rodwell, starting his first match since the 3-1 home win over QPR on Sept. 1.
Chelsea, starting just 64 hours after its draw in Prague on Thursday night, rang the changes, with Demba Ba returning to the side in place of Fernando Torres.
The visitors looked jaded in the first half as City poured forward in droves and at times threatened to tear them apart.
The hosts’ main tactical ploy was to target the right side of Chelsea’s defense and free up either Gael Clichy or David Silva on the overlap to launch a cross on to the head of one of their powerful on-rushing midfielders.
Rodwell, in particular, made a series of excellent runs into the box and his height was a real danger to the opposition. The former Everton man could have had a hat trick in the opening half but Chelsea held firm through a combination of last-gasp defending, the safe hands of Cech and some mixed finishing.
Five minutes into the second half, a Chelsea long ball sent Ba bearing down on the City goal. Despite being covered by Kolo Toure, Hart came rushing out to harass the Senegal striker, who left his foot in and was taken down by the England No. 1.
The award of a penalty was debatable but it could easily have been avoided by Hart. With the criticism of Mancini no doubt ringing in his ears, the keeper atoned for his error of judgement by flinging himself low to his right to keep out Lampard’s spot kick.
Ten minutes later, City’s supporters had even more reason to celebrate. Yaya Toure collected the ball from Silva in the box, surged past two defenders and, confronted by the presence of Gary Cahill, opened up his body to guide a wonderfully composed finish past the grasp of Cech. It was a quite stunning goal, combining the power of a bulldozer with the precision of a surgeon.
The game opened up as Chelsea searched for an equalizer but Benitez’s team were too sloppy in possession to cause City much angst.
The home side were rewarded for their perseverance with a second goal after 85 minutes. Silva was once again the goal-maker, laying on the ball for Tevez to line himself up for a thunderbolt strike past Cech.