Chelsea suffered their first defeat under coach Jose Mourinho on Saturday when the English Premier League title contenders went down 1-0 at lowly Manchester City.
An 11th-minute Nicolas Anelka penalty caused the upset at the City of Manchester stadium and left champions Arsenal five points clear at the top after they had cantered to a 3-1 win over Aston Villa earlier in the day.
Previously unbeaten in both Premier League and Champions League action, Chelsea were taken by surprise by a City side who had only won two of their previous eight league games and had flirted with relegation last season.
That defeat leaves Arsenal top on 25 points with Chelsea second on 20 and Everton a point further back after a late 1-0 win over Southampton. Manchester United slipped to sixth, 11 points adrift of Arsenal, after a 0-0 draw at Birmingham City.
Asked about his first defeat, Mourinho told Sky Sports: "You have to accept it. The game is over, they got the three points and we go home with zero."
Mourinho, who disagreed with the penalty decision, added: "We deserved more from this game...we missed some easy chances and (City goalkeeper) David James deserved his Man of the Match award."
The late kickoff had an electrifying start when Anelka raced into the penalty area and was bundled over by the last defender Paulo Ferreira, a member of Mourinho's Champions League-winning Porto side last season.
Ferreira was booked rather than red-carded as the French striker was heading away from goal but Anelka made no mistake from the spot.
MISSING DROGBA
Both sides had chances in an end-to-end second half, with England winger Shaun Wright-Phillips tormenting Chelsea down the right and Frank Lampard forcing a finger-tip save on to the post by City's deposed England keeper James.
Deprived of injured striker Didier Drogba, Chelsea failed to score on a day that Jimmy Floyd Hasselbaink, offloaded by the west Londoners in the close season, grabbed a hat-trick for Middlesbrough in a 4-0 win at 10-man Blackburn Rovers.
Bolton Wanderers are fourth (15 points) after a disputed Kevin Davies header gave them a 1-0 win over Crystal Palace, Middlesbrough are a point behind and Liverpool are seventh (13 points) after coming back from two down to beat Fulham 4-2.
Few managers will have ended the day in as good a mood as Arsenal's Arsene Wenger.
Five points clear, his side extended their record unbeaten league run to 49 matches and will try to reach 50 against bitter rivals Manchester United at Old Trafford a week on Sunday.
Their display on Saturday left Wenger purring.
"It was an unexpected start but from then on I felt we developed some fantastic play," he said.
"We created chance after chance but their keeper (Stefan Postma) was a hero today. We needed to be steady, stubborn with our game. We did it very well. It was very enjoyable to watch."
Arsenal trailed to a third-minute strike by Lee Hendrie but a 19th minute penalty from Robert Pires made it all square, Thierry Henry put them ahead just before halftime and Pires sealed the win with his second of the day.
United manager Alex Ferguson was able to field his four first-choice strikers -- Ruud van Nistelrooy, Alan Smith, Wayne Rooney and Louis Saha -- together for the first time this season at Birmingham.
But Van Nistelrooy missed their best chance in the first half and the home side merited a point. "You have to give credit to them," Ferguson conceded.
At Craven Cottage, Portuguese forward Luis Boa Morte put Fulham 2-0 up against Liverpool at halftime.
Two Milan Baros efforts, one of which flew in off Fulham defender Zat Knight, levelled the scores before Liverpool's Spanish defender Josemi was sent off.
But Xabi Alonso, with a fine free kick, and fellow substitute Igor Biscan made it 4-2 in a frantic finish to secure Rafael Benitez's team a first away league win of the season.
(Additional reporting by Bill Barclay)