Manchester United 1-6 Manchester City
Man United's defence has been unconvincing so far this season, and their vulnerability was finally, and brutally exposed by their bitter, and now dangerous, local rivals.
City have won derbies over the last decade or so, but previously, those results had little significance beyond the local. At the end of every season, United were hoisting trophies, and City remained a sleeping giant at best.
While the lopsided nature of last Sunday's scoreline is largely due to the dismissal of Jonny Evans with the score at 0-1, it is, nonetheless, very impressive. United have had numerous difficult spells during Ferguson's long reign. But no team has previously had the talent or the balls to come to Old Trafford and hand them such a whipping. Circumstances played a big part, but boy did City take advantage of their opportunity to lay down a marker.
Just how significant will the game prove to be?
It should send City's confidence sky-high. They already have the best squad of players in the league, and are playing the best football (despite their manager's reputation for negativity). They are rightful favourites, at this point, to win the title.
But United under Ferguson have the handy habit of turning adversity to their advantage. One would expect them to be just as galvanised by their own humiliation as City are by their moment of glory.
With that said, there are deficiencies in the United team that were cruelly exposed by their neighbours and this has surely shot some holes in the aura that often allows United to coast through games against lesser sides. Their relatively ordinary central midfield and a defence that has been unsettled by changing partnerships and by an apparent decline in the performances of its senior members are primary concerns.
They do not have a player with the creative flair of David Silva, or indeed a player with the destructive zeal of Nigel De Jong who, frighteningly enough, City don't even seem to need at the moment.
The evidence is that if United are to make it title number twenty, they will need to rely on their neighbours' oft-showcased appetite for self-destruction.
David Silva was the star again. His imperious volleyed pass through to Dzeko for the final goal has garnered much of the attention, but he was involved in so much. He has that admirable habit, like Bergkamp before him, of making the players around him look better. He attracts the attention of defenders, and that frees up space for others, and he has the vision, technique and selflessness to help those other players exploit the space fully. Witness the build up to Balotelli's second goal, and how Silva waits and releases to Milner at just the right time.