Arsenal stunned Premier League leaders Chelsea at Stamford Bridge Sunday as two Robin van Persie goals earned the Gunners a 2-1 victory.
Johan Djourou's own goal gave Chelsea a halftime lead but Dutchman van Persie struck twice in three second-half minutes as Chelsea slid to a second home league defeat of the season.
Champions Manchester United are now just five points behind Chelsea with a game in hand after they won 1-0 at Manchester City despite having Cristiano Ronaldo sent off. Wayne Rooney poached United's winner just before halftime.
Tottenham Hotspur were beaten 1-0 at home by Everton while Portsmouth beat Blackburn Rovers 3-2 at Fratton Park.
Liverpool can now move three points clear at the top of the table Monday if they beat West Ham United at Anfield.
Arsenal manager Arsene Wenger had refused to concede that his side's title challenge was over despite five league defeats and a 10-point deficit to the leaders.
The Frenchman's claims seemed wildly optimistic after 31 minutes when Arsenal went behind. Goalkeeper Manuel Almunia was guilty of a careless throw-out and after Chelsea won possession Jose Bosingwa's cross was turned in past Djourou.
Chelsea, already beaten at home by Liverpool, should have added to their lead before and after halftime with Frank Lampard twice going close.
Arsenal were going nowhere until the 59th minute when Chelsea failed to clear and an offside-looking Van Persie turned and smashed a shot past Petr Cech.
There was no doubt about Van Persie's second as he spun on the edge of the area and hit a low left-foot shot past Cech into the corner of the net.
United manager Alex Ferguson would have cheered Van Persie's contribution after his side deservedly won the Manchester derby with Wayne Rooney's 100th club goal.
"We needed three points today because we are chasing," Ferguson told Sky Sports. "This was a significant result today."
Rooney scored a tap-in three minutes before halftime after Michael Carrick's shot had been parried into his path by City goal keeper Joe Hart.
United had to play the last 23 minutes with 10 men after Ronaldo was shown a second yellow card when he inexplicably met a corner using his hands rather than his head and referee Howard Webb deemed it to be gamesmanship.
The Portuguese winger looked bemused as he reluctantly trudged off, indicating that he thought the referee's whistle had been blown before he handled the ball.
Ferguson, who is soon to serve a touchline ban for abusing a referee, was guarded when asked about the Ronaldo red card.
"I've seen it again and in actual fact he's tried to protect the ball from his face," Ferguson said. "He thought he heard the referee's whistle, but I'm not going to get into the referee because I could be here all day."
United dominated to such an extent that it would have been an injustice if Richard Dunne had equalised for City in stoppage time -- his shot cleared off the line by Patrice Evra.
Rooney almost grabbed a spectacular second after Dunne's near-miss for City. With Hart up supporting City's attack, United broke out an Rooney's audacious lob was clawed away by the keeper who ran the length of the pitch to regain his ground.