The Premier League title race was thrown wide open Sunday thanks to leader Chelsea's shock 3-0 home defeat to Sunderland and Arsenal's hard-fought 2-1 win at Everton.
Chelsea's 100 percent home record ended as a solo effort by Nedum Onuoha and second-half goals by strikers Asamoah Gyan and Danny Welbeck earned Sunderland a deserved victory. They were the first goals the Blues have conceded at home this season.
Bacary Sagna and Cesc Fabregas were Arsenal's scorers at Goodison Park, with Tim Cahill's 89th-minute consolation coming too late for Everton.
Arsenal is now just two points behind Chelsea, with third-place Manchester United - which drew 2-2 at Aston Villa on Saturday - a further point behind. Manchester City is fourth, six points behind the leaders, after drawing at home to Birmingham on Saturday.
Chelsea's makeshift defense, which was missing first-choice center backs John Terry and Alex, was ripped apart by Sunderland's lively attacking display, and manager Carlo Ancelotti acknowledged Sunderland was a worthy winner.
"Everything went wrong," Ancelotti said. "We didn't play well or how we wanted. Sunderland played with fantastic spirit, fantastic pressure.
"It was a bad day. We were not able to play our football, just 15 minutes in the first half. Everything was difficult today, it was a strange performance."
It was Chelsea's heaviest home defeat since April 2002 and its second loss in three league matches, having been beaten 2-0 at Liverpool last Sunday.
Since going down to an embarrassing 5-1 defeat at northeast neighbor Newcastle on Oct. 31, Sunderland has picked up seven points from a possible nine to move up to sixth place.
"Two weeks ago, we were hung, drawn and quartered," Sunderland manager Steve Bruce said. "We were looking for a response and got it. They have worked very hard to get over the Newcastle defeat.
"It was the worst performance of my career two weeks ago and today was arguably the best."
Paulo Ferreira, usually a right back, was played out of position in central defense alongside Branislav Ivanovic for Chelsea, and the pair were all at sea.
Onuoha opened the scoring in the last minute of the first half when he waltzed around two defenders before slipping a left-footed shot past Petr Cech for his first goal for Sunderland.
Gyan took advantage of more holes in the Chelsea defense by making it 2-0 in the 52nd, finishing off a flowing move involving Boudewijn Zenden, Welbeck and Jordan Henderson by curling his finish around Cech.
Chelsea did not seriously threaten Sunderland goalkeeper Craig Gordon and conceded a third, in the 86th, when Welbeck pounced on Ashley Cole's wayward back pass and guided a low finish past the stranded Cech.
Arsenal has bounced back from a 1-0 home defeat to Newcastle last Sunday by winning two straight away games, the victory at Everton following a 2-0 success at Wolverhampton Wanderers on Wednesday.
"We've had two difficult away games but we have got six points and that puts us in a good situation. The team has shown great spirit," Arsenal manager Arsene Wenger said.
Sagna scored a rare goal when the France right back smashed a shot into the roof of the net at the near post in the 36th.
Fabregas doubled Arsenal's lead three minutes into the second half after exchanging passes with Marouane Chamakh before steering a low shot into the far corner.
Everton piled the pressure on in the final 20 minutes but found goalkeeper Lukasz Fabianski in inspired form.
Cahill managed to find a way past the Poland international in the 89th when the Australia international bundled in from close range after Louis Saha had headed down a corner at the far post.
"I can't really feel as if we deserved an awful lot. I don't think we played all that well," Everton manager David Moyes said. "I didn't think Arsenal were great and I don't think we were."
