Chelsea and Arsenal shared the points on offer in Tuesday's London derby after a 2-2 Premier League draw at Stamford Bridge.
The hosts were gifted the lead after David Luiz was shown a red card for fouling Tammy Abraham in the box, allowing Jorginho to score a 26th-minute penalty.
Arsenal were back in the game when Gabriel Martinelli ran the length of the field to produce a calm finish after 63 minutes.
Frank Lampard's men turned the screw in the closing stages, with captain Cesar Azpilicueta believing he'd scored the winner with six minutes remaining.
However, there were celebrations from the away side three minutes later when Hector Bellerin found the bottom corner.
A tepid first half saw the visitors fail to hit the target before half-time, but the Blues also struggled to make their advantages pay.
The game burst into life when Arsenal's defence gifted the advantage as Shkodran Mustafi's mistake received a double punishment.
The German's poor pass to Bernd Leno allowed Abraham to intercept and beat the goalkeeper, only for Luiz to bring down the striker before hitting the target.
The former Chelsea defender was shown a red for his challenge, and Jorginho made it 1-0 from the spot. The disastrous moment underlined the depth of Arsenal's defensive problems, and new manager Mikel Arteta will be concerned by the alarming issues at the back.
The 10 men were under pressure either side of half-time but survived Chelsea's attempts to pick the lock a second time.
With the Blues in the ascendancy, the game was flipped on its head after a stunning counter-attack from Arsenal levelled the contest.
A Chelsea corner saw Arteta's forward line break away. N'Golo Kante slipped on the halfway line, allowing Martinelli a one-on-one with Kepa Arrizabalaga. The 18-year-old produced a finish beyond his years, calmly slotting past the stopper after running from the edge of his box with the ball at his feet.
It was a moment of magic from the prodigy, but Kante's error was the catalyst for the ice-cold finish.
The drama continued until the end of the game, and both sides' fragility was highlighted before the Gunners earned a point.
Lampard will be disappointed with how his team gave away the win, and it seemed the three points were sealed for the hosts when Azpilicueta scored.
A short corner confused the Arsenal defence, and as the ball found its way into the box, the Blues defender was allowed to fire home.
To Arsenal's credit, they were not beaten after suffering defensive calamities. The visitors put together a late run of positive possession to earn a second equaliser.
Bellerin moved into the box from the right-back position, and his left-footed effort beat Kepa inside the far corner.
Arteta celebrated with his coaching team and substitutes, but this was an encounter Chelsea should've closed out with relative ease.
Both teams are set to feature in FA Cup's fourth round. The Blues travel to Hull City on Saturday, while Arsenal are away at Bournemouth on Monday.