Chelsea 1 Sunderland 2: Blunders from veteran goalkeeper Mark Schwarzer and full back Cesar Azpilicueta allowed Sunderland to inflict Jose Mourinho's first home league defeat as Chelsea manager and hand Liverpool control in the Premier League title race.
Schwarzer marred his league debut for Chelsea, with Petr Cech suffering a virus, by gifting Sunderland striker Connor Wickham his third goal in a week.
Azpilicueta then upended Jozy Altidore to hand former Chelsea player Fabio Borini the penalty that secured success, with Chelsea incensed by a host of refereeing decisions and coach Rui Faria sent to the stands.
Mourinho had to drag Faria away from fourth official Phil Dowd as the hosts' protests turned ugly after Sunderland stole the late lead.
Chelsea’s defeat means leaders Liverpool can open up a four-point advantage over the second-placed Blues with victory at Norwich on Sunday.
Basement club Sunderland climbed within one point of 19th-placed Fulham, following up their 2-2 midweek draw at Manchester City with another impressive result on the road.
Samuel Eto'o's 14th goal of the season proved fruitless for Chelsea, with midfielder Ramires facing a premature end to his campaign if he faces punishment for appearing to strike Sunderland's Sebastian Larsson in the face.
The FA's disciplinary department will be likely to review footage of the incident, able to impose sanctions given referee Mike Dean took no action during the match.
Ramires’s two red cards this season could see him receive a five-match ban.
Chelsea’s insistence on elaborate approach play limited their first-half opportunities, leaving the hosts frustrated to be level 1-1 at the break.
Nemanja Matic and Willian failed to trouble Sunderland goalkeeper Vito Mannone from early efforts, before Eto'o stole into the Sunderland box only to have the ball nicked off his toe by Santiago Vergini.
The Cameroon poacher was not to be denied from the corner however, side-footing home on the volley after Willian’s delivery.
Notions of a Chelsea victory march were quickly trampled by Wickham’s tap-in equaliser.
Chelsea had only themselves to blame for conceding just their 10th home league goal of the season, their back four retreating far too deep from Larsson’s corner.
Marcos Alonso had acres of space to tee up a drive on the edge of the area, but his effort should never have troubled Schwarzer.
The 41-year-old spilled what should have been a routine save, however, gifting Wickham his third league goal of week after his midweek brace at the Etihad Stadium.
Not even captain John Terry’s despairing lunge could deny Wickham, leaving the hosts to nurse a rare but self-inflicted Stamford Bridge wound.
Oscar chipped a curling shot on target form the edge of the area as Chelsea rallied, but Mannone was wise to it, and that sequence was repeated from a direct free-kick just moments later.
Terry had the ball in the back of the net just past the half-hour as the hosts battled for supremacy, only for Matic's penalty-box foul on Jack Colback to deny the captain.
Mannone almost handed the lead back to Chelsea when flapping Branislav Ivanovic’s header onto his own crossbar.
The Italian goalkeeper was able to smother the ball at the second attempt though, denying the hosts further dead-ball dividend.
Mannone parried Matic's 20-yard shot before denying Mohamed Salah on the rebound.
Borini’s clearing header struck team-mate Alonso’s arm in the Sunderland area, but Dean rightly waved away penalty appeals.
Willian strode clean through for Chelsea next, only for Mannone to produce another inspired stop, before Ramires was bustled off his cue by Larsson when aiming to head into the empty net.
Dean took no action, allowing play to continue, and moments later Ramires meted out his own brand of retribution by flinging a stray arm into Larsson’s face just yards away from the referee.
Sunderland winger Adam Johnson raced into the Chelsea box as time ticked down on the half, only for Terry to nip in and pinch the ball off his toe just as he was about to strike for goal.
After all the first-half bluster, Chelsea roared into a gilt-edged chance for Eto’o after the restart.
Willian cantered clear on the counter, teeing up the Chelsea striker at the perfect moment, only for Eto’o to clip the shot just wide.
Willian then cut the ball back into the path of substitute Demba Ba, only for the former Newcastle striker to swing at fresh air with the goal gaping.
Replacement Fernando Torres injected immediate pace into counter-attacking proceedings, before firing high above the bar with an overhead kick and forcing a corner from another effort.
The ex-Liverpool man then headed straight at Mannone after a lumped ball into the box.
Azpilicueta then felled Altidore in the box after slipping and failing to recover, handing Sunderland a penalty.
Borini coolly slotted the spot-kick for his first goal in eight games, to heap the pressure on Mourinho’s title-chasing men.
Faria was sent to the stands after his overzealous protest and Chelsea were unable to make five minutes of added time count, condemning Mourinho to his first defeat in 78 league games at Stamford Bridge.
