Chelsea's championship challenge was dented as they suffered their first defeat of the season at Manchester City.
Jose Mourinho's side looked anything but title contenders as they fell five points adrift of leaders Arsenal after City recorded a long overdue home victory against their opponents.
Nicolas Anelka's early penalty proved decisive earning City their first success on home soil against Chelsea since 1990-91 season.
City had suffered five straight home defeats against Chelsea, but ended that miserable sequence after a battling display which proved they can mix it with the best.
But it must once again have been frustrating for City manager Kevin Keegan proving to him how his side has massively under-achieved in the past 12 months.
City capitalised on a slip on the wet surface by Chelsea left-back William Gallas which proved instrumental in the move which led to them being awarded a 10th minute penalty.
City broke forward and Paulo Ferreria was adjudged to have pulled back Anelka as he burst through on goal.
The Portuguese defender was lucky only to be booked because it could easily have been a red card produced by the referee Howard Webb.
Anelka stepped forward to score from the spot, his sixth goal of the season, which was only the second Chelsea had conceded in nine Premiership matches.
City played with plenty of spirit, chasing and harrying and Chelsea were unable to get into their stride.
Indeed, City goalkeeper David James only had two serious saves to make in the first period.
And of those, only one caused him any degree of difficulty as Frank Lampard's free-kick took a wicked deflection off the defensive wall, but James managed to keep out the shot with his legs.
Mourinho, who had been animated throughout the half, stood on the touchline, evidently had words with his players at the break as they came out with a purpose and determination not seen in the first 45 minutes.
They noticeably upped the tempo and took the game to City who were forced on to the retreat from the re-start.
Lampard, who scored in Manchester one week earlier for England in their World Cup qualifier against Wales, led the assault.
The midfield maestro thumped a long-range drive which James managed to turn on to the post low to his right.
Lampard then fired in another long distance effort which James, flinging himself to his left, brilliantly turned round the post for a corner.
The same player then had a third shot at goal in a six-minute spell but this time his shot cleared the crossbar.
City had to rely on counter attacks and on one rare forward sortie Shaun Wright-Phillips shot agonisingly wide.
City weathered the storm and created a number of clear cut chances in the closing stages.
Their fans were convinced they had scored a second goal in the 73rd minute when Wright-Phillips cut the ball back from the right and Jon Macken fired into the sidenetting.
There was an enormous roar as many fans in the ground thought Macken had found the net.
Chelsea had a great opportunity to draw level nine minutes from the end when Icelandic international Eidur Gudjohnsen, in front of goal, pulled a shot disappointingly wide when you would have thought he should have hit the target.
Man of the Match: Frank Lampard - Worked tirelessly to try and rescue his side but was unable to crown another fine midfield display with a deserved goal.