Sergio Aguero, Vincent Kompany and Fernandinho compounded further embarrassment to Jose Mourinho by getting on the scoresheet to inflict a heavy away defeat and leave the champions five points behind City after just two games.
Man City were imperious in the clash of heavyweights yet their performance will be overshadowing by Mourinho's ongoing row with the medical team as for the second week in-a-row the Blues were temporarily down to nine-men after Gary Cahill and Diego Costa were taken off the pitch in the first-half with head injuries. At the restart captain John Terry had been replaced by Kurt Zouma - the first time the 34-year-old had ever been substituted by Mourinho.
Team doctor Eva Carneiro did not make the journey to the Etihad whilst team physiotherapist Jon Fearn was around the stadium but was not on the bench.
Before Aguero opened the scoring, the 2014/15 Golden Boot winner had four shots within the first 30 minutes but stand-in goalkeeper Asmir Begovic had the better of the exchanges with a string of superb saves. Leading to the Argentine giving his opponent the thumbs up.
Aguero's frustrations did not last longer however as he netted in the 32nd-minute by controlling David Silva's pass and moving into the box before slotting the ball past Begovic after it bounced in off the past.
Prior to the match Mourinho had only ever lost once against Man City (in October 2004 when Kevin Keegan was in charge) but the Citizens kept up the pressure and once Kompany broke free off Branislav Ivanovic to head in Silva's corner for the second game in-a-row in the 78th-minute, the Portuguese looked consigned to a second defeat against last season's runner-ups.
It was the first time since December 2013 the Belgium international had scored in back-to-back games in the Premier League, suggesting a return to form after a poor campaign last time out.
Despite Mourinho's claims the best side in the second-half lost, but the only goal they scored was an offside tap-in by Ramires and it took Chelsea until the 70th-minute to register their first shot on target. Their best chance fell to Diego Costa who hit the woodwork as he dived to poke the ball. However, in the 93rd-minute that effort at most would have been a consolation.
The defeat means Chelsea have failed to win their first two games in the Premier League for the first time since 1998 and it equals their heaviest defeats under Mourinho - Middlesbrough in 2006 and West Brom in 2015. Incidentally, the Blues play West Brom next, whilst Man City go away to Everton.