Jose Mourinho suffered his first Premier League defeat since returning to Chelsea following a 1-0 loss against Everton at Goodison Park.
Mourinho's men were guilty of missing a host of chances and were made to pay for their wastefulness when Steven Naismith grabbed the winner on the stroke of half-time to hand Roberto Martinez his first Premier League victory as Everton manager.
Debutant Samuel Eto'o and Andre Schurrle were particularly guilty of missing good opportunities for Chelsea in the first half.
And Naismith pounced from Nikica Jelavic's header back across goal in first-half injury time.
Substitute Oscar felt he should have been awarded a penalty in the second half but referee Howard Webb waved away the protests.
Mourinho handed a first competitive start to transfer window signing Eto'o, with Fernando Torres dropping to the bench.
Everton gave a debut to Gareth Barry but fellow new boy James McCarthy had to settle for a place among the substitutes.
In a lively opening, Eto'o almost opened his Premier League account as early as the fourth minute.
Ramires found space on the right and his pin-point cross was met by the Cameroonian but he could only head over the bar from eight yards.
At the other end, Jelavic was equally as wasteful. Ross Barkley won possession in midfield and he supplied Naismith, whose excellent cross was met by the Croatian but he headed tamely at Petr Cech.
Tim Howard was given a huge reprieve in the 29th minute after a small lull in clear-cut openings.
Howard's attempted pass out of defence was intercepted by Eden Hazard. He centred to Eto'o, who looked destined to tap into the empty goal only to be denied by a wonderful sliding interception from Barry.
Chelsea continued to press and Mourinho was visibly frustrated as two good opportunities were not converted. First, Ramires flicked a ball in the air and volleyed at goal only to be denied by Howard.
The Brazilian then broke free again and prodded into the path of Schurrle, but the German blasted well over when one-on-one with the goalkeeper.
And Chelsea were made to pay for their profligacy in front of goal when Naismith notched the opener on the stroke of half-time.
Barkley crossed to Jelavic at the back post and he headed back across goal to the Scot, who could not miss when heading home on the goal line.
The second half started in similar fashion with Chelsea creating but unable to break down Everton's resistance.
Schurrle broke free but chipped over Howard into the side netting, before Howard parried a Hazard effort into the path of Eto'o but he failed to connect as the ball went harmlessly wide.
Oscar replaced Juan Mata, and the Brazilian thought he should have had a penalty in the 58th minute.
He ran across Sylvain Distin and was felled in the box but Webb was unmoved. Replays suggested Oscar may have had legitimate claims for a spot-kick as he appeared to touch the ball before the Frenchman.
With 20 minutes remaining, the lively Ramires stretched for a Branislav Ivanovic cross but he could only fire into the side netting.
Everton looked threatening on the counter attack as Chelsea searched for the equaliser and had a series of corners before Kevin Mirallas had an effort beaten away well by Cech.
The home fans thought their team had a late penalty when Seamus Coleman was brought down by Hazard, but the incident occurred just outside the box.
And they came desperately close to a second in the 88th minute when Leighton Baines saw his free-kick rebound off the crossbar.
|Coach: Roberto Martínez|
for N. Jelavić 66'
for S. Naismith 89'
for K. Mirallas 90+2'
|Chelsea ´warehousing´ players - PFA chief|
|United States 2 Peru 1: Altidore inspires hosts´ comeback|
|Del Bosque unmoved by calls for two strikers|
|Deschamps praise for beautiful France|
|Fekir ruptures knee ligaments|
|Italy v Bulgaria: Conte warns against complacency|
|Euro 2016 Qualifiers Review: Germany top Group D, Northern Ireland edge closer|
|Low: Three points most important|
|Northern Ireland on the verge of a ´magnificent achievement´ - O´Neill|
|Scotland need something against Germany - Strachan|
|Portugal 0 France 1: Late Valbuena set-piece clinches deserved win|
|Faroe Islands 1 Northern Ireland 3: O´Neill´s men edge closer|
|Germany 3 Poland 1: Gotze sends world champions top|
|Gibraltar 0 Republic of Ireland 4: Irish hopes reignited|
|Djibouti 0 Togo 2: Saintfiet´s side make it two wins from two|
|Cyprus v Belgium: Benteke boost for Wilmots´ men|
|Roma youngster faces lengthy lay-off|
|United hit back at Perez barb over De Gea saga|
|Georgia 1 Scotland 0: Strachan´s men succumb to Tbilisi hoodoo|
|Hodgson prepared to blood new players|
|Porto invite Euro elite to help raise millions for migrants|
|Dortmund legend Dede backs Tuchel to succeed|
|Robben out for four weeks|
|Turkey v Netherlands: Terim expecting hostile atmosphere for crunch clash|
|Portugal 0-1 France: Valbuena strikes late to sink Ronaldo & Co|
|Wales v Israel: Euro 2016 beckons for Coleman´s history boys|
|Gala: No extra payment for Grosskreutz|
|Increase Bundesliga´s TV rights or be left behind - Rummenigge|
|Kane: I´m no flash in the pan|
|Perez: United showed inexperience in De Gea saga|
|Milligan: Socceroos wary of Tajikistan|
|Conte wants more players like Pelle|
|OFC World Cup Qualifying Review: Samoa to meet Tahiti in next round|
|Krychowiak stayed at Sevilla because of Emery|
|I never considered Bayern exit - Gotze|
|Balotelli ´not in good condition´, Milan must improve - Mihajlovic|
|Robben slams ´stupid´ Martins Indi|
|Robben laments injury blow|
|Euro 2016 Qualifiers Review: Bale edges Wales closer, Iceland dent Netherlands´ qualification hopes|
|De Bruyne relieved to ´boss´ Bosnia-Herzegovina|
|Blind furious after nightmare debut|
|Coleman sees shades of Charles in Bale winner|
|Conte only concerned about Italy winning|
|Mauritania v South Africa: SAFA to investigate Masilela no-show|
|AFC World Cup Qualifying Review: Qatar hit 15 in Bhutan rout|
|Belgium 3 Bosnia-Herzegovina 1: De Bruyne shines in straightforward victory|
|Cyprus 0 Wales 1: Bale winner takes Wales one step closer|
|Netherlands 0 Iceland 1: Sigurdsson winner caps difficult first game for Blind|
|Italy 1 Malta 0: Pelle spares wasteful Azzurri|
|Balotelli stars in Milan friendly win|
|Bhutan thrashed 15-0 by Qatar in qualifier|
|Rwanda v Ghana: Gyan doubt gives hosts hope|
|Tanzania v Nigeria: Enyeama out of AFCON qualifier|
|Valdes and Berahino included in Premier League squads|
|Costa Rica v Brazil: Dunga´s men return after Copa disappointment|
|Spain v Slovakia: Azpilicueta eyeing important revenge|
|Adebayor left out of Tottenham squad list for league and Europe|
|San Marino v England: Place in history books beckons for Rooney|
|Germany can cope with Reus absence - Low|
|Bayern offer aid to refugees in ´training camp´|
|BREAKING NEWS: Welbeck ruled out for months after knee surgery|
|South Korea 8 Laos 0: Son leads the way in rout|
|Australia 5 Bangladesh 0: Socceroos surge to emphatic win|
|Japan 3 Cambodia 0: Hosts pick up first qualifying win|
|Rudiger aiming to nail down Euros spot after Roma move|
|Melo happy to join Inter at last|
|Hernandez thanks Ferguson after United departure|
|Chung: AFC has compromised FIFA election|
|Wales the new best of British|
|Reus out of Germany qualifiers|
|Chile v Paraguay: Vidal missing for Copa champions|
|Ghedin: Anything is possible for Malta|
|Pogba will be worth €100m - Marotta|
|England can win Euro 2016 - Hodgson tells players|
|Conte unsure over Balotelli future|
|Argentina - Bolivia Preview: Mascherano backs 'very special' Messi|
|Portugal - France Preview: Deschamps aiming to correct mistakes|