Arsenal risk being cut adrift in the Premier League title race after a humiliating 6-0 defeat at Chelsea in Arsene Wenger's 1,000th match as manager on Saturday.
Wenger described the result as “one of the worst days” of his career and his misery was compounded by subsequent victories for title rivals Liverpool and Manchester City that saw his side slump to fourth place.
Luis Suarez scored a hat-trick as Liverpool won 6-3 at Cardiff City to move to within four points of Chelsea, while City are two points further back -- but with three games in hand -- after Yaya Toure also claimed a treble in a 5-0 win over Fulham.
Arsenal were left seven points off the pace, albeit with a game in hand, after Wenger's side were blown away by a flurry of first-half goals from Samuel Eto'o, Andre Schurrle, Eden Hazard and Oscar at Stamford Bridge.
Hazard's goal came from the penalty spot after Arsenal midfielder Alex Oxlade-Chamberlain had handled the ball on the line, but a peculiar case of mistaken identity meant that his team-mate Kieran Gibbs was sent off instead by referee Andre Marriner.
Oscar completed his brace in the 66th minute before substitute Mohamed Salah scored to seal the club's biggest ever win over Arsenal and give manager Jose Mourinho his most emphatic Chelsea success.
“This defeat is my fault. I take full responsibility for it,” said a crestfallen Wenger who then chose not to attend his post-match press conference.
“I don't think there's too much need to talk about the mistakes we made. We got a good hiding today.”
Mourinho, whose side had crashed to a 1-0 defeat at Aston Villa last weekend, said: “At 2-0 after seven minutes, the game is over. We were too strong.
“We had momentum, but it stopped last Saturday against Aston Villa for some reason. Now we are trying to build more momentum.”
Chelsea remain top, but Liverpool are hot on their heels, and have a game in hand, after twice coming from behind to overwhelm second-bottom Cardiff in south Wales.
Ole Gunnar Solskjaer's side threatened to pull off an upset by going ahead through Jordon Mutch in the ninth minute and then retaking the lead through Fraizer Campbell after Suarez had equalised.
Centre-back Martin Skrtel equalised in the 41st minute, however, and Suarez's two second-half strikes, allied to goals from Skrtel and Daniel Sturridge, secured a sixth successive victory for Liverpool, with Mutch replying for Cardiff.
Suarez now has 28 league goals for the season, just three short of the record for a 38-game campaign.
City moved above Arsenal into third place after Toure's treble helped to put paid to bottom club Fulham, who had defender Fernando Amorebieta sent off early in the second half.
Toure's first two goals came from the penalty spot and he completed his first City hat-trick with an effortless 25-yard curler before Fernandinho and Martin Demichelis added two late goals.
Sunderland remain in the bottom three, albeit with two games in hand on the sides immediately above them, after a Robert Snodgrass goal and an Alexander Tettey blockbuster saw them go down 2-0 at Norwich City.
Norwich were the only team in the bottom seven not to lose, which enabled them to climb seven points clear of the relegation zone.
Papiss Cisse's 94th-minute header saw fourth-bottom Crystal Palace lose 1-0 at Newcastle United, while West Bromwich Albion remain 16th after a 2-0 loss at Hull City.
Liam Rosenior put Hull ahead in the 31st minute, with former West Brom striker Shane Long adding a second goal seven minutes later.
Swansea City, meanwhile, fell 3-2 at Everton, who moved above Tottenham Hotspur into fifth place.
Leighton Baines, Romelu Lukaku and Ross Barkley found the net for Everton, with Wilfried Bony and Ashley Williams on target for the visitors.
Later on Saturday, seventh-place Manchester United will hope to harness the momentum from their 3-0 victory over Olympiakos in the Champions League in mid-week when they visit West Ham United.