Chelsea have fallen to their first loss at Stamford Bridge in the Premier League under Jose Mourinho having been defeated 2-1 by Sunderland.
The Blues took the lead early on through Samuel Eto'o, but Sunderland hit back with goals from Connor Wickham and Fabio Borini to take all three points.
The first opportunity of the contest fell to the home side after just four minutes, when Willian's strike was punched away by Vito Mannone.
Chelsea managed to break the deadlock shortly after when Eto'o met Willian's corner, volleying into the back of the net from close range.
Sunderland managed to find an equaliser just six minutes later, however, with Mark Schwarzer fumbling Marcos Alonso's effort, leaving Wickham to convert the rebound.
Oscar saw his free kick saved by Mannone on the half-hour mark, while the Italian shot-stopper also kept out Branislav Ivanovic moments later.
There was to be a controversial moment before the interval when Ramires appeared to lash out at Sebastian Larsson, but the incident was not seen by any of the officials.
The Blues were dominating possession in the opening stages of the second half, but were unable to create any real openings, with Fernando Torres coming closest with his spectacular overhead kick which sailed over the bar.
Then, with eight minutes remaining, Jozy Altidore was brought down by Cesar Azpilicueta in the area with the referee awarding the Black Cats a penalty. Borini stepped up to take the spot kick and made no mistake, giving his side the lead.
Emanuele Giaccherini very nearly added a third goal for Gus Poyet's side late on, but his long-range drive narrowly missed the target.
The result means Sunderland are now within three points of safety, while Liverpool remain two-points clear at the top of the league table with a game in hand over Chelsea.