Chelsea squandered the chance to go five points clear at the top of the table as goals from Nedum Onuoha, Asamoah Gyan and Danny Welbeck gave Sunderland a shock 3-0 win at Stamford Bridge.
Onuoha put the visitors ahead on the stroke of half-time with a wonderful individual goal and Gyan added the second early in the second half.
Welbeck set the seal on a dreadful Chelsea performance when he intercepted Ashley Cole's backpass in the 87th minute and coolly slotted home.
In the 18th minute Chelsea managed to fashion their first real chance when John Mikel Obi put Nicolas Anelka in the clear but he could not control it in time and the opportunity went begging.
Chelsea goalkeeper Petr Cech kept the scores level in the 36th minute when Onuoha crossed for Welbeck to head the ball towards the bottom corner. The Czech keeper dived low to his left to turn the ball around the post.
But after Cech made another superb double save, Onuoha dribbled through the Chelsea defence to put Sunderland in front. It was the first goal Chelsea had conceded at Stamford Bridge since they hosted Aston Villa in March.
Chelsea's afternoon got worse in the 52nd minute when Sunderland opened up their defence once more and Gyan added the second. Jordan Henderson collected the ball from Welbeck and put Gyan clear, and the Sunderland striker made no mistake as he slipped the ball beyond Cech.
Chelsea were now rocking and unable to cope with Sunderland's quick passing and movement. In the 59th minute Welbeck sent a curling effort just wide of the far post as the visitors threatened to add to their lead.
The home side had rarely threatened in the second-half and Bolo Zenden almost made it three for the visitors when he tried to divert the ball past Cech from close range in the 63rd minute.
And Sunderland made it three in the 87th minute when Chelsea defender Cole's poor back pass was intercepted by Welbeck and the striker kept his cool to beat Cech.