Arsenal almost pay for flimsy start but remember they are in a derby just in time
Chelsea 2-2 Arsenal
Perhaps it was a touch of complacency after their win against Man City before the international break. Perhaps it was Jorginho caught in the headlights on his return to Stamford Bridge. Maybe it was the incessant rain. Whatever it was, Arsenal were awful for 50 minutes and almost paid the price.
Their unbeaten league record was in real danger of being blown out of the water and the confidence they had been doing so well to nurture looked as though it was about to be unceremoniously undermined.
Somehow, they got out of jail, with two goals in seven minutes repairing the damage. Declan Rice and sub Leandro Trossard were the heroes of the hour after a collective improvement that had not appeared on the cards.
They went into their evening clash with the Blues on the back of six wins out of the past seven meetings with them, but it was the Blues who began as if scenting blood.
They were all over the Gunners, who were so off the tempo set by Mauricio Pochettino's men that it was a wonder they were only a goal down at the break.
Hungrier, sharper, and pressing relentlessly, this Chelsea looked like a team rather than the collection of individuals they have been up to now in this campaign.
The hosts were good at applying a tourniquet of pressure but the Gunners seemed to wilt under the examination. Were they aware it was a London derby? Their sloppy, listless response to the opening salvos were feeble in the extreme.
Yes, the intervention by VAR official Jarred Gillett was pathetic. His decision to flag up William Saliba's handling of a cross from Raheem Sterling was ridiculous because the ball deflected onto the defender's arm as he went up with Mykhailo Mudryk, whose header touched it onto the offending limb. But Chelsea were worthy of their lead - Cole Palmer having put away the spot-kick.
Ah yes, Mudryk. The man who was all-but buying his Arsenal shirt for Instagram posts before Chelsea approached him. What a day the Ukrainian had. Probably his best since the switch to west London.
His start at Stamford Bridge has been underwhelming, to put it kindly, but today he decided to be effective, as if to further punish the visitors for failing to sign him.
Having won the penalty in the first half, he scored with a dipping shot over David Raya from an angle to make it 2-0 soon after the break. A better reflection of the balance of play. It seemed to shock the Matthew Harding faithful as much as Arsenal's defenders.
Raya was arguably at fault for the goal and almost gifted another with a casual roll out to Palmer. On days like today, it feels perverse that Aaron Ramsdale was ever axed.
Arsenal finally started to play in the opposition half, and managed to reduce the arrears when Robert Sanchez's stray pass out from the back invited Declan Rice to ping it straight past him.
Could that be the springboard the Gunners needed? Up to now, only Gaby Martinelli's work down the left had caused Chelsea serious worries but now it was the turn of the returning Bukayo Saka to do his bit - his angled cross from the right evading defenders to find an onrushing Trossard at the far post. His stab home sent away fans wild.
There is nothing quite like the unexpected and slightly underserved result against a bitter rival.
They finished strongest too, with another sub, Eddie Nketiah, almost bagging an incredible winner. Triumphant seasons are often built on crazy days like this. Mikel Arteta must hope it is a lucky omen.