Fabian Delph's late winner saw Aston Villa deal a huge blow to nine-man Chelsea's Premier League title hopes with a shock 1-0 triumph.
The midfielder showed a brilliant piece of ingenuity in the 82nd minute to turn home substitute Marc Albrighton's centre and hand Paul Lambert's side all three points at Villa Park.
Jose Mourinho had stated that Manchester City were favourites to lift the Premier League crown during the week, and there was an element of truth to the Chelsea manager's words as his side failed to break down a resolute Villa defence.
There could have been a different outcome had Nemanja Matic's effort on the stroke of half-time not been ruled out for handball.
But Chelsea's indiscipline ultimately cost them - Willian was shown a red card for a second bookable offence in the 68th minute before Ramires was also dismissed in injury time following a crude challenge on Karim El Ahmadi.
Chelsea still retain a six-point lead over second-placed City, though Manuel Pellegrini's men have three games in hand to cut the gap, while Villa's win lifts them to 10th.
Chelsea had Villa largely pinned back in their own half in the opening 10 minutes, but the visitors were almost exposed by a Villa counter-attack that ended with Christian Benteke heading Delph's cross wide.
Mourinho's men were comfortable in possession, however, with Oscar looking particularly lively - the Brazilian curling a shot just wide after 15 minutes as he ventured forward.
After a promising opening, the game suffered something of a lull, but it was Chelsea who continued to look the more likely to score and Fernando Torres fired wide from a tight angle after a neat throughball from Eden Hazard after 35 minutes.
Villa's biggest threat was on the counter, and the lively Benteke saw an acrobatic half-volley from the right-hand side of the box fly wide of the far post.
The home side then had a huge let off five minutes before the break. Willian's corner was flicked to the back post by John Terry, where Matic squeezed the ball home - only for referee Chris Foy to rule the goal out for a handball by the Serbia international.
Chelsea continued to dictate the tempo after the break, and Villa goalkeeper Brad Guzan had to make a smart reaction stop when El Ahmadi directed Hazard's cross towards goal when sliding to make a block.
The second half followed a similar pattern to the first, with Chelsea continuing to probe but failing to find a way through a stern Villa rearguard.
Villa retained a foothold in the game, and Benteke should have done better when he received a pass from Andreas Weimann on the edge of the area and placed a shot narrowly wide of Petr Cech's goal.
With just over 20 minutes remaining Chelsea were reduced to 10 men. Willian - who had already been booked in the first half - was rash in pulling back Delph and was shown a second yellow card, although the decision was perhaps harsh on the Brazilian.
The hosts made the most of their numerical advantage when Albrighton's cut-back from the byline went behind Delph, but the midfielder somehow flicked home.
Delph then went close to a second when his shot was deflected onto the crossbar by Terry, before Chelsea's match ended in further ill-discipline when Ramires was sent off for a lunging tackle on El Ahmadi, while Mourinho was sent to the stands for his protests.
|8||K. El Ahmadi|
|Coach: P. Lambert|
for G. Agbonlahor 74'
for J. Bennett 78'
|Dunga unfazed by pressure|
|Montenegro fan turns himself in after flare incident|
|Injured Messi not ready - Martino|
|Hodgson: Rooney not close to Charlton|
|Terim proud of Turkey|
|Hiddink happy with point|
|Euro 2016 Qualifying Review: Netherlands and Italy stage late escapes|
|Debutant Eder delighted with Azzurri bow|
|Argentina 2 El Salvador 0: Mancuello nets debut goal in straightforward win|
|Kovac not satisfied despite Croatia victory|
|Netherlands 1 Turkey 1: Huntelaar spares Hiddink from historic home loss|
|Ghana 1 Senegal 2: Konate brace downs Black Stars|
|Bulgaria 2 Italy 2: Controversial debutant Eder rescues Conte´s men|
|Morocco 0 Uruguay 1: Cavani spot-kick seals win|
|Al Sadd say talks with Xavi ongoing|
|McClean slams Sunderland´s handling of poppy controversy|
|Ghana 1-2 Senegal: Black Stars continue Afcon hangover|
|Cheltenham player diagnosed with cancer|
|Palace takeover talk premature - Parish|
|Odegaard becomes Euro qualifiers´ youngest starter|
|Job not done yet, Bale warns Wales|
|Israel 0 Wales 3: Brilliant Bale bags brace as Wales go top|
|Dunga backs Neymar to overhaul Pele´s Brazil goal record|
|League Two Review: Hartlepool climb out of drop zone, Cheltenham go bottom|
|El Salvador 0-2 Argentina: Martino's men triumph without Messi|
|League One Review: Canavan leaves it late to deny County|
|Freddy Adu signs with 11th team in as many years|
|Besiktas deny Cech, Danny rumours|
|Puerto Rico v Canada: Haber targets more momentum|
|Miranda not contemplating Atletico exit|
|Austin relaxed over England prospects|
|Manchester United should sign Ibrahimovic - Schmeichel|
|Ibe eyes Liverpool run-in|
|Bertrand called up by England as withdrawal of four players confirmed|
|A-League Review: Risdon nets stunner, Germano tames Roar|
|Panama v Costa Rica: Unbeaten run a secondary concern for Wanchope|
|Italy coach Conte shaken after death threats - FIGC chief|
|Barca fears over Alba eased|
|Schweinsteiger to start Germany qualifier|
|Akinfeev thanks fans after flare incident|
|Injuries offer Kane chance of first England start|
|Russian Football Union to protest following Montenegro abandonment|
|October comeback the target for injured Foster|
|Van der Vaart looks set to leave Hamburg|
|Bale focused on Wales - Coleman|
|Kluivert helps Curacao to victory|
|Hamstrung Alba returns to Barcelona|
|Macedonia v Australia: Confident visitors eye victory|
|Akinfeev to return to Moscow with Russia squad|
|Brnovic: Montenegro have no chance of qualifying|
|Russia had to resume after Akinfeev incident - Capello|
|Terim: Robben absence important|
|Brazil - Chile Preview: Winning is 'our only option' - Dunga|
|France - Denmark Preview: Olsen hits out at 'disrespectful' hosts|
|Morata keen to keep working|
|Canada 1 Guatemala 0: Haber heads Floro´s men to win|
|Difficult to find a place for Kane in starting XI - Hodgson|
|Difficult to find a place for Kane in starting XI - Hodgson|
|Montenegro-Russia abandoned after scuffle|
|Euro 2016 Qualifying Review: Montenegro-Russia abandoned, Spain and England win|
|Accrington Stanley 0 Newport County 2: Visitors up to sixth|
|Kane delighted with ´dream´ start|
|England 4 Lithuania 0: Kane enjoys dream debut|
|Spain 1 Ukraine 0: Morata settles tight contest|
|Akinfeev struck by flare as Montenegro-Russia game suspended after 30 seconds|
|Brazil v Chile: Winning is ´our only option´ - Dunga|
|Northern Ireland v Finland: Controversial fixture met with religious protests|
|Scotland v Gibraltar: Wilson out to dent countrymen´s hopes|
|Republic of Ireland v Poland: Pressure is on, says O´Neill|
|Georgia v Germany: Schneider warns world champions|
|PSV agree permament Guardado deal|
|France v Denmark: Olsen hits out at training facilities|
|Pienaar to return to Everton training|
|Hughes eyes silverware at Stoke after signing new deal|
|Portugal v Serbia: Carvalho vows to attack|
|Dynamo Kiev stadium partially closed after racism probe|
|Hull City fined £30,000 for misconduct|
|Balotelli must work hard for Italy return – Bonucci|
|Marchisio suffers knee ligament injury|
|Hughes agrees new Stoke City deal until 2018|
|Martinez hopeful over injured Everton trio|
|South Korea 1-1 Uzbekistan: Kuziboyev's debut strike denies hosts|
|South Korea 1 Uzbekistan 1: Kuziboyev´s debut strike denies hosts|
|Japan 2 Tunisia 0: Kagawa and Honda shine as Halilhodzic starts with a win|
|South Africa v Nigeria: Mashaba wary of bitter opponents|
|Japan 2-0 Tunisia: Kagawa & Honda shine in Halilhodzic's first game|
|Parma captain Lucarelli welcomes FIGC reforms|
|South Africa - Nigeria Preview: Mashaba wary of bitter opponents|
|Di Francesco ignoring Milan rumours|
|Melbourne Victory 2 Central Coast Mariners 1: Finkler leads fightback|
|Bale would be ´perfect´ for United - Scholes|
|Badstuber and Bellarabi out of Georgia clash|
|Rooney KOs boxing celebration|
|Allen thrilled with Welsh ´hunger´|
|Kovacic to miss Euro 2016 qualifier|
|Costa Rica 0 Paraguay 0: Dour draw marks Diaz debut|
|Reid ruled out of South Korea friendly|
|Deschamps talks up France despite defeat|
|Rooney chasing England goalscoring record|
|Brazil ´superior´ admit French veterans|
|Reeves sidelined for Finland clash|
|Confidence critical for rampaging Brazil - Dunga|