Arsenal hammer dismal Chelsea
Goals from Alex Song, Cesc Fabregas and Theo Walcott in a nine-minute spell either side of half-time condemned Carlo Ancelotti's team to another defeat and they have now managed just six points from the last 24 on offer.
Branislav Ivanovic replied for the visitors but the damage was already done as Arsenal ended a run of five consecutive defeats against their London rivals to reclaim second place in the table above Manchester City on goal difference.
"The win had a double impact. First of all it keeps us in touch with the leaders and, secondly, it is the pyschological impact because we were questioned about our ability to win big games," Arsenal manager Arsene Wenger told reporters.
"We know that to beat the big teams at home will have an important impact on the league (title race)."
Arsenal have moved to 35 points from 18 games with unbeaten leaders Manchester United on 37 having played a game less. Chelsea, who started the season in scintillating form but have forgotten how to win, remain in fourth place on 31.
"The table is not good but this is the reality," said Chelsea manager Carlo Ancelotti. "We have to play better and wake up. I am not worried. I have to work and you will have to ask the owner (Roman Abramovich about my future)."
After an unofficial two-week "winter break" caused by the freezing weather conditions in Britain, both sides knew a win was needed to stay in touch with Manchester United.
Chelsea had been impressive in the second half of their 1-1 draw at in-form Tottenham Hotspur 15 days ago and, with Frank Lampard in the starting lineup for the first time since August, there was optimism among the visiting fans that their season could be reignited at a ground that has been kind to them.
However, after 40 minutes of cut and thrust had failed to separate the teams, Chelsea fell apart alarmingly, leaving Ancelotti ashen-face in the technical area where he had stood in a black raincoat for virtually the entire 90 minutes.
If anything Chelsea had looked the more threatening early on with Didier Drogba, scorer of 13 goals in 13 appearances against Arsenal since joining Chelsea, rampaging forward to fire narrowly wide of Lukasz Fabianski's post.
Arsenal's home form has been an irritant this season with three defeats already at Emirates Stadium and there were anxious grumblings around the stadium as their pretty possession football offered little goal threat.
In the end it took some direct action from midfield enforcer Song to lift the psychological shackles Arsenal manager Arsene Wenger feared had begun to grip his side against Chelsea.
A minute before half-time the Cameroonian barrelled forward, played a one-two with Jack Wilshere and, as the ball bobbled back into his path, tucked a low show past Petr Cech.
Six minutes after the break Chelsea imploded.
Michael Essien's attempt to win the ball in midfield inadvertently sent Walcott racing through on goal and the Engla