Yaya Toure and Carlos Tevez took advantage of a rare Frank Lampard penalty miss to fire Manchester City to their first Barclays Premier League win in a month.
Lampard was a kick away from his 200th Chelsea goal when he lined up a second-half spot-kick at the Etihad Stadium but Joe Hart, who stayed on after fouling Demba Ba, saved from his England team-mate.
Yaya Toure made Chelsea pay with a fine finish and substitute Tevez made the 2-0 victory certain with a long-range effort late on. The result reduced Manchester United's lead at the top of the table to 12 points and increased City's advantage over third-placed Chelsea to seven.
City had their first shot within 40 seconds as Yaya Toure took aim from the edge of the area but Petr Cech saved easily. It was some time before Chelsea threatened, but after initially being beaten, Kolo Toure recovered well to cut off Ba's counter-attack.
Despite their early dominance, it was 15 minutes before City really tested Cech as Matija Nastasic went forward for a corner but the goalkeeper dealt with the Serbian's powerful header. Jack Rodwell had a shot blocked by Gary Cahill and David Silva played in Sergio Aguero but the Argentinian overran the ball.
Aguero pulled back a James Milner cross and Pablo Zabaleta's powerful volley was headed away by Cahill. Rodwell then tested Cech twice in just over a minute, first forcing the keeper to tip over a powerful 25-yard drive and then heading into his arms from the resulting corner.
The game's pivotal moment came in the 50th minute as City switched off at the back and Ba raced on to a long ball from deep. Ba shrugged off Kolo Toure and clipped the ball past the out-rushing Hart but was brought down as he got tangled in the goalkeeper's legs.
Referee Andre Marriner immediately pointed to the spot but importantly felt Ba was just moving away from goal and did not show Hart a card. Hart made the most of the reprieve to earn instant redemption by saving from Lampard, who had scored his last 10 spot-kicks, low to his right.
Roberto Mancini opted to replace the influential Rodwell with Tevez as the game opened up. Milner then found Silva in the box with a clever reverse pass and his pull-back found Yaya Toure on the edge of the area. The Ivorian touched past two defenders and curled a superb low finish beyond Cech and in at the far post.
Chelsea made a double change in response with Lampard making way along with Eden Hazard for Victor Moses and Oscar. It was not long before Torres was introduced for Mikel. But Tevez made the most dramatic impact, putting the game beyond the visitors with a superb strike from outside the area five minutes from time.
