After handing Chelsea the title on Friday, Roberto Mancini watched his Manchester City side promptly snatch it away again as Carlos Tevez's second-half strike ended the champions' 100% record with a 1-0 win.
In a tactical battle, Tevez's moment of inspiration just before the hour proved to be decisive. Chelsea were unable to halt his burst from halfway and he found the perfect finish too, through Ashley Cole's legs and in off the post.
Chelsea battled hard to force an equaliser, but, just as they had done for most of the contest, they failed to open up City and came no nearer than the header Branislav Ivanovic struck the bar with before half-time.
Only once were the Blues opened up properly. Tevez drifted away from Florent Malouda as he anticipated a return pass to Didier Drogba, who had just taken a corner and his movement gave Malouda the space to curl a deep cross to the far post, where Alex nodded it back to Ivanovic who could only find the woodwork.
After Ivanovic's near miss, the first two minutes of the second period produced as much intense action as there had been in the whole of the first.
After Joe Hart had pushed a curling Nicolas Anelka shot away from danger, Michael Essien should have done far better with the near-post corner than send his header sailing over.
City responded with their first meaningful assault on the Chelsea goal, which forced Petr Cech to make a decent save to deny David Silva.
It proved to be the prelude to the deadlock being broken. It was mainly the South American's own work as he ran ferociously at the visitors' defence, jinked to his right, then blasted a shot through Cole's legs and into the net off the inside of the post.
Alex glanced a header wide but with Cole also belting a shot into the side-netting, Chelsea ran out of ideas.