City juggernaut brought to a shuddering halt by Mourinho's warriors
Chelsea outlined their credentials as genuine title contenders by muscling their way past favourites Manchester City with typical power.
Manager Jose Mourinho had claimed he was preparing his side for a challenge next season but few believed him and, mind games or not, Branislav Ivanovic's solitary strike means his team are now well and truly in the hunt for Barclays Premier League honours, level with second-placed City and only two points behind Arsenal.
Mourinho's methods may come in for criticism but he does know how to set up a team to get a result and Chelsea's approach in the first half of this 1-0 win was spot-on.
Many predicted they would come and "park the bus" as they had done in a dour encounter the last time they were in Manchester across the city at United.
But that was not the tactic in which became the first side to end City's 61-game run of scoring at home in the league stretching back to November 2010, when a less-celebrated Birmingham team achieved the same feat.
Central defender David Luiz playing the holding role in midfield alongside Nemanja Matic gave the four players in front them freedom to press, harry and hurry their City opponents.
Eden Hazard led the attack but the relentless running of Willian and Ramires ensured Chelsea, while maybe not playing the best football, posed the greater threat.
City, without injured leading scorer Sergio Aguero, created a number of half-chances but the visitors looked the more likely to score and ultimately did.
City's midfield powerhouse Yaya Toure made his presence known in the penalty area, firing one shot over and then driving past Matic to set up David Silva to whip a shot across goal and wide of the far post.
Chelsea, who had already had the ball in the net when the excellent Hazard squared for Samuel Eto'o only for the Cameroonian to be flagged offside, regularly counter-attacked with verve and venom - which is a trait familiar to Mourinho teams.
How they did not score when Willian found himself four-on-two after Martin Demichelis lost the ball deep in Chelsea territory at a City corner was a mystery.
The Brazilian probably held onto the ball for too long and most definitely picked the wrong option of Ramires to his left, with Hart punching away his shot, with experienced striker Eto'o to his right.
City's goalkeeper could do nothing about Ivanovic's thunderous 32nd-minute strike though, with the Serbian smashing home left-footed after Ramires' shot had been blocked by Vincent Kompany.
The ever-dangerous Hazard tested Hart low to his left before skipping past right-back Pablo Zabaleta with ease and crossing for Eto'o - who hit the bar.
City, well off their game, were fortunate to be only one down at half-time and although Toure drilled wide from Dzeko's lay-off early in the second half Chelsea continued their relentless pursuit of their prey.
Stevan Jovetic replaced Alvaro Negredo, the 23-goal striker having barely had a touch never mind a chance, but Dzeko could equally have been the one to make way.
Mourinho continued to prowl his technical area making minor adjustments, with the instructions increasingly pragmatic as they looked to hold on to their lead, happy to let his side continue to counter from deep and threaten at set-pieces.
Matic hit the bar from distance and Gary Cahill headed against a post at a corner but the onus was placed firmly on City to come and break them down.
Silva's curling free-kick had Petr Cech scrambling to his left to tip over, before the Spain international bundled a shot wide when he should have hit the target.
Mourinho was enraged when last defender Matija Nastasic was only booked for hauling down substitute Oscar on the halfway line but it was not a pivotal decision.
That had been made by the Portuguese himself with his pre-match planning, seeing his side become the first team to do the double over City since Everton in 2010-11.
Cech's save from Jovetic and Nastasic's sliced volley, both in added time, summed up both Chelsea's resilience and City's frustration.