Arsenal performed a late collapse as Chelsea snatched a 2-1 win at the Emirates.
The Gunners were in control for the majority of the game after Pierre-Emerick Aubameyang's first-half opener.
But Bernd Leno failed to collect a free-kick with his howler allowing Jorginho to tap in an equaliser less than 10 minutes from time.
Tammy Abraham then slotted in the winner moments later as Mikel Arteta's first home game in charge unravelled in dramatic circumstances.
Here's how the players rated from both sides as Chelsea's poor performance ended with a shock victory against their London rivals.
Arsenal player ratings
Bernd Leno - 5 - Had a stinker on Chelsea ’s equaliser - totally misjudged the cross.
Ainsley Maitland-Niles - 7 - Booked. Tenacious, did much better and confidence is clearly returning.
Calum Chambers - 6 - Desperate blow as he went off injured having made excellent start.
David Luiz - 7 - Booked. Looked on a mission against his former club.
Bukayo Saka - 6 - Better than at Bournemouth as he stayed deeper and just defended.
Matteo Guendouzi - 6 - Booked. Looked a liability at times, clumsy and careless. A worry.
Lucas Torreira - 8 - Booked. Hallelujah! Played in his best position for a change - and was terrific.
Reiss Nelson - 7 - Battled hard down the right wing, one of his liveliest games yet.
Mesut Ozil - 7 - Stylish, dictated play and battled hard. Yes, really. Got standing ovation.
Pierre-Emerick Aubameyang - 7 - Scored and was even tracking back to make challenges. Better attitude.
Alexandre Lacazette - 6 - Booked. Devoid of confidence but at least he battled. Conceded silly fouls.
Substitutes:
Shkodran Mustafi (for Chambers, 23) - 6
Joe Willock (for Ozil, 75) - 6
Nicolas Pepe (for Nelson, 86) - 6
Chelsea player ratings
Kepa Arrizabalaga - 6 - Not much he could do about Arsenal goal, fairly quiet afternoon.
Antonio Rudiger - 7 - Booked. Chelsea look better with him, battled on with big head bandage.
Kurt Zouma - 7 - An unsung hero this season, the glue which holds the defence together.
Fikayo Tomori - 6 - Struggled early on and then switched to right back in reshuffle.
Cesar Azpilicueta - 7 - Started at wing back, switched to full back, solid throughout.
N'Golo Kante - 7 - Booked. He got through so much work in defence and attack.
Mateo Kovacic - 5 - Could not make the desired impact and was substituted early.
Emerson Palmieri - 5 - Lost Aubameyang on opening goal, sacrificed for tactical reshuffle.
Willian - 8 - MotM. Worked hard, created problems and no wonder he set up the winner.
Mason Mount - 7 - Booked. Showed aggressive side of his game. Supplied free kick on leveller.
Tammy Abraham - 7 - Arsenal did well to keep him shackled for so long - and then he pounced at end.
Substitutes:
Jorginho (for Emerson, 34 mins) - 7
Lamptey (for Tomori, 59 mins) - 6
Hudson-Odoi (for Kovacic, 70 mins) - 6
