Chelsea suffered a shock defeat and their first home loss in the Premier League this season when Sunderland beat them 3-0 thanks to goals from Nedum Onuoha, Asamoah Gyan and Danny Welbeck on Sunday.
Onuoha became the first opponent to score against Chelsea in the league at Stamford Bridge this season with a memorable goal just before halftime when he weaved past three Chelsea defenders and fired wide of goalkeeper Petr Cech.
Sunderland, beaten 7-2 at Chelsea last season, doubled their lead after 52 minutes when a brilliant move involving Welbeck and Jordan Henderson, called up to the England squad for the first time, found record signing Gyan who gave Cech no chance.
Welbeck added the third in the 87th minute after a rare mistake by Ashley Cole who overhit a backpass to Cech, completing one of the most unexpected scorelines of the season.
The upset left champions Chelsea, who were without first-choice centre-backs John Terry and Alex, top of the table on 28 points, two ahead of Arsenal who won 2-1 at Everton.
Manchester United, who fought back to draw 2-2 at Aston Villa on Saturday after trailing 2-0, are third on 25 points.
Sunderland moved up to sixth after ending a run of 11 successive defeats by Chelsea dating back to 2001.
Arsenal move up to second spot
Goals from Bacary Sagna and Cesc Fabregas gave Arsenal a 2-1 win at Everton on Sunday to lift them above Manchester United into second place in the Premier League.
Fullback Sagna, with only his second goal for Arsenal in more than 140 matches, opened the scoring when he fired past Tim Howard at the near post after 36 minutes. Fabregas added the second goal three minutes into the second half.
Arsenal, who thrashed Everton 6-1 at Goodison Park on the opening day of last season, dominated for much of the game but had to hang on at the end after Tim Cahill scored for Everton in the dying minutes.
It was Everton's first defeat for eight League matches. They had plenty of chances of their own with Cahill missing a good opportunity with an early header and Jermaine Beckford thwarted after coming on as a 69th-minute substitute for Phil Neville.
Everton's late rally had Arsenal rocking but goalkeeper Lukasz Fabianski also saved well from Steven Pienaar and Louis Saha to prevent the home side equalising.
Arsenal boss Arsene Wenger told the BBC: "It's always very difficult to come here and that is three very important points, based on great spirit, great resilience, more than style.
"These are very important ingredients to be successful. You need those qualities to win the title. The team deserves a lot of credit," he added.
Everton boss David Moyes said: "Overall I can't have any complaints. One or two decisions could have gone the other way but it didn't go for us. I don't think either team were at their best but we never really got hold of the game and we weren't able to generate an atmosphere inside the ground which we normally do."
