Chelsea surrendered another three points in their quest for a top-four Premier League finish as Newcastle United's new signing Moussa Sissoko struck in the last minute to grab a 3-2 win that left Rafa Benitez's side reeling.
It was another late horror show for third-placed Chelsea, who had led 2-1 with goals from Frank Lampard and Juan Mata before capitulating for the second time in a week, having conceded twice in the dying minutes at Reading on Wednesday.
With fourth-placed Tottenham Hotspur in action on Sunday, Everton had the chance to move above them but drew 3-3 at home to struggling Aston Villa, who led 3-1 before Marouane Fellaini's double spared Everton's blushes.
Lukas Podolski scored in the 78th minute to hand Arsenal a 1-0 victory at home to Stoke City, a result that helped the Gunners close in on the Champions League qualification places.
Leaders Manchester United were aiming to move 10 points clear of Manchester City when they met Fulham in the late kickoff at Craven Cottage.
Any thoughts of pushing the Manchester clubs in the title race are long gone for Chelsea, who have now managed just one win from their last six games in all competitions - a run that will increase the pressure on interim manager Benitez.
The Spaniard said his side should have been awarded a penalty and the hosts reduced to 10 men after striker Demba Ba, signed from Newcastle last month, was left bloodied by a clash with Fabricio Coloccini after trying to turn in a rebound.
"It was a penalty and a red card," Benitez told Sky Sports, saying Ba, who was replaced by Fernando Torres, had suffered a broken nose.
"If it had been in the middle of the park it would have been a free kick and maybe a yellow but in the area it's a penalty and red because it was a clear chance."
Worryingly for Chelsea, they appear to be running out of steam and conceding late goals as the season reaches a critical point in their hopes of a top-four finish.
That was the case again on Saturday as Sissoko turned the match on its head after Chelsea had seized control.
Jonas Gutierrez gave Newcastle the lead after 41 minutes with a header but Chelsea replied after the break with Lampard's fierce shot and a curler from Mata.
Former Toulouse midfielder Sissoko, one of several French signings for Newcastle during January, tapped in an equaliser after 68 minutes after Chelsea keeper Petr Cech had parried Papiss Cisse's shot.
'PAYING US BACK'
Sissoko then crowned a superb home debut when he crashed home a 90th-minute winner after a cut-back from Davide Santon.
"I remember watching him for Toulouse 14 months ago, and I thought he was the one for us," Newcastle boss Alan Pardew said.
"We accelerated (the deal) because he was going to come in the summer and he's paying us back handsomely."
Chelsea remain in third place with 46 points from 25 games, with Tottenham in fourth spot on 42 points from a game less.
Everton also have 42 with Arsenal in sixth on 41.
David Moyes's Everton seemed to be slipping to only their fourth league defeat of the season after Christian Benteke's double helped Villa into a 3-1 lead at Goodison Park.
However, Fellaini took the game by the scruff of the neck, scoring with a low shot 20 minutes from time and then heading an equaliser in the third minute of stoppage time.
At the bottom of the table a missed penalty from Adel Taarabt cost relegation-threatened Queens Park Rangers victory against Norwich City as they drew 0-0 at Loftus Road.
QPR's fourth league draw in a row meant they are now six points from safety after Reading beat Sunderland 2-1.
Southampton drew 2-2 at Wigan Athletic, meaning none of the six sides at the bottom of the table before kickoff lost.
West Ham United beat Swansea City 1-0 thanks to a goal from on-loan Liverpool striker Andy Carroll.
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