At 2-2 on 60 minutes, this was a tense but hugely engaging game that could have gone either way. Few, however, would have predicted the direction it ultimately took. Impressive creativity gave way to utter chaos.
At the end of it all, the only objective 'fact' we have is that the European champions have finally lost in the league. Almost everything that led to that outcome, though, is up for intense debate.
There was a comeback, two contentious red cards, a number of other incidents that went untouched, a hugely controversial refereeing performance, an injured steward, a heated touchline debate, an official complaint about the referee and, ultimately, a very dubious winning goal. At least, no-one was talking about handshakes.
And, in truth, all those discussion points ensured there were almost as many dimensions to this game: what it says for the title race, what it says about teams and, ultimately, what the last half-hour says about the state of the game. After all that, it wasn't just the result and repercussions that were almost forgotten amid all the furore but the fact Manchester United actually reversed two conspicuous recent trends: they went ahead rather than behind early on, before suffering from a comeback.
What that points to is one of the few things we can say with any degree of certainty beyond the fact of the final score: both these teams are superb going forward but hugely suspect at the back.
Before this match, it had occasionally seemed like Chelsea's poor defensive game had been disguised by a series of forgiving league fixtures, as well as the implosion of Arsenal and absences at Tottenham.
That was borne out within three minutes as their under-protected backline was pulled all over the place and Robin van Persie's strike against the post fortuitously went in off David Luiz. For the next half-hour, it looked like Manchester United would score every time they went forward. Indeed, it only took them eight minutes to do so again. And, if the first was fortunate, this was an impressive show of force.
As has happened on a few occasions between these teams now, Antonio Valencia bested Ashley Cole, United's movement unravelled Chelsea and Van Persie entered the void to finish. If United looked rampant, though, it was partly because the home side's defensive structure was in ruins.
As Shakhtar Donetsk's Fernandinho indicated on Tuesday and as Di Matteo himself all but admitted on Friday, Chelsea's main problem is that they may be very quick to counter-attack but are worryingly slow to re-organise. When they have the ball, for example, the two centre-halves often go very wide in order to play it out. The big issue with that is, unlike say Sergio Busquets at Barcelona, no midfielder properly drops back in order to fill the gap. Here, John Obi Mikel often looked 20 yards more advanced than he should have been.
It's an issue they're going to have to solve. On Sunday, at the least, a reprieve came in the fact United have a very similar issue.
Although Michael Carrick is positionally excellent and frequently showed Chelsea how their defensive formation should have looked, he doesn't have the presence to make it properly count. Too many times, a challenge was too weak or a move bypassed him. A telling example came when he appeared to win the ball of Eden Hazard only for the Belgian playmaker to show greater strength and come out on top.
A telling moment occurred when the free-kick from which Juan Mata scored came in exactly the area Carrick should have been patrolling. Here, of course, the otherwise impressive Wayne Rooney deserves criticism given how he wildly swung at Hazard. Mata took advantage in absolutely perfect fashion. A divine free-kick.
By then a Chelsea goal had seemed thoroughly inevitable. From the very moment United seemed to properly retreat at around the half-hour mark, it appeared a serious error. They didn't have the defensive fortitude to hold steady.
Once the second half started, it looked like the only way United were going to quell the barrage was to go for another goal themselves. Instead, it was no surprise when Chelsea's cast of creators reversed the pattern of the opening minutes of the first half and completely unravelled United for Ramires to head home the equaliser.
From there we had a perfect case study of the kind of psychologies and dynamics that govern these games. Because, having been in a position where they were absolutely dominant, Chelsea suddenly tightened up.
The game immediately returned to a rather tense face-off for the first time since the second minute. And, after a compelling first hour in which all of the game's box-office stars - Mata, Hazard, Van Persie, Rooney - had admirably illustrated their abilities, it looked like we were in store for a compelling showdown and quite possibly the game of the season.
Then, it turned. Instead, we endured the type of chaos that skews everything and tells us nothing. Amid all that, though, it should not be forgotten that the last act from when the game was still a fully-complemented contest was an exquisite Van Persie turn and through ball to set up Ashley Young.
Under contact from Branislav Ivanovic, though, the winger went downwards. So, subsequently, did the quality of the match.
Six minutes later, Chelsea were reduced to nine men. Twelve minutes later, Javier Hernandez won the game. Out of all that, two points should be clarified. First of all, Di Matteo himself admitted Ivanovic probably deserved to be sent off. Secondly, Sir Alex Ferguson conceded that the winning goal was hugely fortunate, given that Hernandez was clearly offside.
It's the in-between, however, which is all open to so much heated discussion. Because, while Chelsea may well have still had a chance to win the game with 10 men, being reduced to nine effectively negated it as a contest altogether. And the main question is whether Fernando Torres should have been sent off.
Despite the fact it ultimately seems harsh, not even multiple replays could lead to a definitive conclusion either way. From there, all we can do is outline the multiple caveats.
First of all, there was Torres' initial yellow card, a pretty abrasive challenge on Tom Cleverley. Secondly, there was Johnny Evans' challenge. Contact was made. Of that there is no doubt. What is up for discussion, though, is the extent of it and whether every mistimed tackle is a foul and every mis-step a dive. Because, just as it was difficult to make out how much contact there was, it was equally tough to make out whether Torres theatrically threw himself to the ground after the incident, merely lost his balance or was outright fouled.
If all that doesn't prove whether it was a truly a second yellow, though, it does lead to two important conclusions. For one, it's unfair to criticise referees for making potentially defining decisions on split-second views, particularly when multiple replays don't reveal the truth.
Two, however, if Mark Clattenburg is not 100% sure that Torres has dived then it is very wrong to send him off. For that, the referee deserves criticism.
Similarly, Di Matteo wasn't so much critical of the individual decisions but aggrieved that all of the borderline decisions appeared to go United's way.
"It's a shame that a game like this has to be decided in that manner... the key decisions were wrong, and all in favour of the opposition," he said.
Ultimately, the table still just about favours Chelsea. They lead by a point. This game seemed to come quite close to answering whether they're complete enough a team to stay there until the end of the season... before opening up an array of other questions.