Arsenal get the blues as Diego seals it for Chelsea
Arsenal 0 - Chelsea 1
It just had to be Diego Costa, the pantomime villain who has spent most of the season sulking and under-performing, who delivered the blow which reawakened all of Arsenal's self-doubt and exposed their shortcomings as potential champions.
Just when Arsenal had the opportunity to bury their Chelsea ghost, to put the belligerent bullies from Stamford Bridge well and truly in their place, they fell short.
Arsenal lost having played the game with 10 men for over 70 minutes following Per Mertesacker's dismissal for fouling Costa. But then Arsène Wenger's reaction to Mertesacker's red card, by withdrawing Olivier Giroud and persisting with the off-form Mesut Özil for 90 minutes, contributed to his team's defeat. It was as though the sight of Chelsea's blue shirts had affected Wenger's thinking.
The end result was the defeat which keeps Leicester City on top of the table and left Arsenal with just two points from a possible nine.
To say Chelsea have failed to perform this season is something of an understatement, but there was a mood of bloody-minded defiance as they set about denying Arsenal the victory which would return them to the top of the league. The message from Chelsea was clear: if you are going to take our crown, you are going to have to earn it.
Costa was the most determined of Chelsea's players and he went toe-to-toe with Laurent Koscielny from the off in an effort to impose himself on the French defender. Koscielny gave as good as he got, but the usually measured Arsenal centre-half allowed Costa to draw him into a physical battle.
After a full-blooded start, Chelsea gained control of the game, with Cesc Fabregas afforded acres of space in the middle third and Willian enjoying the freedom of Arsenal's left flank thanks to the inability of Theo Walcott and Nacho Monreal to work together to nullify the Brazilian's threat.
It was Willian's pace and vision which led to the key moment of the game, when his through ball to Costa released the forward, only for Mertesacker to bring him down clumsily.
Eighteen minutes into the game, referee Mark Clattenburg had no option but to brandish a red card to the German, whose lack of pace was cruelly exposed by Costa before his trailing leg sent him tumbling to the ground.
Wenger chose to substitute Giroud in order for Gabriel to plug the hole alongside Koscielny at the back. It was a bewildering decision. Giroud, in goalscoring form, would have given Arsenal an out ball, a physical presence to shield the ball and alleviate the pressure, yet Wenger instead placed Walcott up front before asking Özil to play the role.
And if Gabriel had been sent on to keep Costa quiet, that move backfired too for Wenger, the centre-half losing the Chelsea striker for the crucial split-second as he raced to the near post to volley Branislav Ivanovic's cross past Petr Cech to make it 1-0.
Chelsea could have extended their lead when Cech saved brilliantly from Costa at the near post on 42 minutes.
Had Giroud remained on the pitch, Arsenal might have scored themselves three minutes later, but a perfect delivery from Aaron Ramsey was inexplicably directed over by Flamini's kung-fu kick volley, when a header was the obvious option.
Arsenal attempted to salvage the game in the second half and the 57th-minute introduction of Alexis Sanchez injected more urgency and ambition. But they were only spared the prospect of going 2-0 down when Clattenburg dismissed Chelsea appeals for a penalty after Koscielny had barged Fabregas to the ground.
Arsenal huffed and puffed until the final whistle without ever truly threatening to score. Three games without a win now. Is this the annual wobble or a minor bump in the road? It is a question that they really did not want to face at the Emirates.