Going into Saturday's game at Stamford Bridge, Chelsea had taken 31 out of the last 33 points available.
It looked like Chelsea's success would continue until their defence unraveled, which resulted in one of the most memorable games I've ever had the chance to witness.
Who was the worst Chelsea player? Read on to find out.
Here are Chelsea's player ratings.
Player rating: 5/10
Petr Čech was beaten at his near post when Theo Walcott scored, and Čech should have done better with Robin van Persie's shot.
Čech will have serious reservations about the back four protecting him, because they offered next to no protection today.
Player rating: 2.5/10
José Bosingwa reaped some joy out of André Santos early in the game, but that was the most joy Bosingwa would have.
The Portuguese's defence is best described by the acronym MIA—missing in action.
Either that or when he is in action, he hardly offers any defence, like watching Santos breeze past him to score and doing the same with Robin van Persie.
Forget about the goals. What about the countless times Arsenal raided a vacant flank that Bosingwa should have occupied?
Yes, there is an emphasis for a right-back to attack, but at the end of the day, the back in right signifies the position as a defensive one.
It's time for Branislav Ivanović to play at right-back.
Player rating: 3/10
Branislav Ivanović was caught napping when Gervinho latched onto a fantastic Aaron Ramsey ball, and from there the Ivorian squared it up to Robin van Persie.
That goal precipitated Arsenal's comeback.
It seems to me that Ivanović has become a better right-back than centre-back.
Player rating: 4.5/10
John Terry's passing out of defence was excellent, as he made 58 of his 61 passes and capitlised on Per Mertesacker's indecisiveness to score just before halftime.
Don't worry about the slip, because it was a pointless and a bad back-pass from Florent Malouda.
Worry about his a defence under his leadership that have been shipping in goals week in and week out.
Player rating: 3.5/10
I do wonder why Chelsea didn't get the ball more to Ashley Cole in order for him to zip past a clueless Johan Djourou, who had no idea what he was doing at right-back.
In the first three minutes, Arsenal's defence was opened up simply by Cole making two pretty smart, but simplistic, runs past Djourou.
Cole was easily beaten several times by Theo Walcott, including the time when the speedster scored, and Cole's defence has really left a lot to be desired this season.
If Patrick van Aanholt has the will to be the best, he'll know this, and he'll step up his game whilst on loan at Wigan Athletic.
Player rating: 7/10
A 97-percent pass rate, two interceptions and three tackles.
John Obi Mikel played his role very well today. He needs to play like this week in and week out.
Ironic that when he does play like this, Chelsea concede five goals.
Yet when he was all over the place against QPR, Chelsea concede one, despite having played the majority of the game with nine men.
Player rating: 8/10
Ramires was excellent, and if people were wondering why Chelsea mounted so many counterattacks in the first half, it was because of the Brazilian's work ethic.
Four interceptions and six tackles. So he won possession from Arsenal 10 times.
Though his trademark lung-bursting runs were missing.
Player rating: 7/10
Frank Lampard provided John Terry with a pinpoint corner and opened the goal-fest by scoring first.
He did give away the ball countless times with Hail Mary passes towards the end of the game, which wasn't needed as Arsenal countered efficiently.
Player rating: 6.5/10
Daniel Sturridge provided a blueprint to opposing sides that André Santos cannot defend. The Brazilian had no answers for Sturridge.
What really let the Englishman down was his inefficiency, especially when he should have squared the ball to Fernando Torres early in the first half.
Player rating: 4.5/10
Fernando Torres was hardly in the game. His best moment was taking advantage of Johan Djourou, but even then the Spaniard couldn't produce the goods.
He attempted six dribbles and lost the ball four times, including twice to André Santos, who was having a horrible game.
One does have to wonder why Torres cannot impact the game like Robin van Persie, because Chelsea midfielders were very good today.
Player rating: 7.5/10
Excellent vision to pick out Frank Lampard, and a great strike.
Though for most of the game Juan Mata drifted in and out.
It really is a problem that he occupies the left flank but doesn't track back at all.
Without possession, Mata should at least have marked Theo Walcott, but the Spaniard's defence isn't his best attribute.
I say play Mata centrally.
I'm not sure if Chelsea manager André Villas-Boas has given Mata a free role, but the Spaniard does drift centrally all the time, which left the left flank open and vacant when Arsenal countered.
Raul Meireles: 4/5*
Impacted the game as he came on. Pressured the Arsenal players and tried to change the game for Chelsea.
Florent Malouda: 0.5/5
Useless. I do not understand why Daniel Sturridge was taken off. To compound the Frenchman's day, he gave John Terry a very bad back pass—so bad that Terry tripped over himself allowing Robin van Persie to score.
Romelu Lukaku: 1/5
Do the Chelsea players think Lukaku is Usain Bolt? Frank Lampard played the Belgian a Hail Mary pass, Fernando Torres played him a horrible through ball when Lukaka wanted the ball at his feet and then Lampard again peppered Lukaku with low-percentage balls.
The only time the Belgian did isolate André Santos, he lost out on the dual.
* substitutes will be rated out of five unless they played in both the first and second half.