Wenger's winless record against Mourinho continues
(Eden Hazard 27-pen, Diego Costa 78)
It was a better Arsenal, it was a smarter Arsenal, but it was a familiar result brought about by a familiar face.
As a tight, tactical encounter swung in the balance, ex-Arsenal captain Cesc Fabregas delivered a 40-metre ball that split his old defence and allowed Diego Costa to strike a decisive second goal.
Once again, Jose Mourinho got the better of Arsene Wenger.
It is the identity of the victor that will hurt the most for Wenger.
It is no secret that the Arsenal manager loathes Mourinho, something that couldn't have been clearer when they clashed on the touchline midway through the first half.
The fireworks began before kick-off, quite literally.
The game was delayed for 15 minutes after Arsenal supporters were reported to have let off flares inside the stadium.
It was an omen of what was to come, for this was a most eventful afternoon.
After an early collision with Alexis Sanchez, Thibaut Courtois was left dazed and apparently briefly unconscious.
In keeping with football's pathetic record on head injuries, the Belgian stopper remained on the pitch for 12 minutes before the sight of blood in his ear finally triggered a substitution and a trip to hospital.
Petr Cech arrived from the bench to take over.
A tight, tactical game turned on a tackle, a rash and dangerous lunge from Gary Cahill that could have broken Sanchez's leg in half.
There was anger on the pitch, but there was even more on the touchline.
Wenger marched up to Mourinho and furiously shoved him in the chest.
Referee Martin Atkinson called them over and told them in no uncertain terms that they would be dismissed if the feud continued.
Continue it did, but only through the coaching staff.
Steve Bould exchanged verbals with Rui Faria.
The stewards gathered nervously, unsure of how to react.
Arsenal had been far more measured and intelligent in their positioning than they tend to be in these sort of fixtures.
Mesut Oezil and Sanchez tried to keep tight to the midfield three, while the fullbacks chose their adventurous moments wisely.
There was little of the cavalier football that traditionally causes them so many problems in the big games.
But, for all their policies of containment, Arsenal had no answer to Eden Hazard.
After 27 minutes, the Belgium forward slalomed through the Gunners' midfield, bursting into the area only to be felled by Laurent Koscielny.
The Arsenal man was fortunate not to be sent off.
Hazard rolled the resulting spot-kick into the corner of the goal as if it was a game of lawn bowls.
The second half was a more subdued affair as Chelsea slowly, but shrewdly, squeezed the life out of the game.
The introduction of Jon Obi Mikel stiffened a midfield that Jack Wilshere had begun to dominate but, as Arsenal began to advance up the pitch, you sensed they were walking into a trap.
One fine ball from Fabrgeas and a ruthless finish from Costa was evidence that they had done exactly that.
The Blues go five points clear at the top and Wenger's miserable record against Mourinho continues.
BY THE numbers
W0 L7 D5
Arsenal manager Arsene Wenger has never beaten his Chelsea counterpart Jose Mourinho in 12 encounters dating back to 2005. He has lost seven and drawn five of the matches.