Manchester City started a deafening rock concert next door with that astonishing 6-1 win at Old Trafford.
Not so much a United blip as a humiliation which will be celebrated on DVD’s and t-shirts by their rivals.
The mental scars could last a long time after what Sir Alex Ferguson called his ‘worst day in football’.
While Jonny Evans’ red card did not help United’s cause, it should not disguise some major concerns for the champions.
The failure to find a world-class midfielder in the mould of a Wesley Sneijder or Bastian Schweinsteiger is coming back to bite Sir Alex.
Just as United’s engine room was totally over-run by Barcelona at Wembley last season, they had no answer to the power of Yaya Toure or the silky brilliance of David Silva on Sunday.
What Fergie would give to have those two in his side.
The fact is, United have never truly replaced Roy Keane’s dynamism and have now lost Paul Scholes as well.
Ferguson has lost faith in Michael Carrick, over-rates Anderson and is forced to rely on the workmanlike Darren Fletcher, with a youthful Tom Cleverly waiting to return when fit.
With injury and age now eroding the Rio Ferdinand-Nemanja Vidic axis, does the manager truly know his best back-four any more?
Further forward, there is clearly a fitness issue with last season’s sensation Javier Hernandez, as he rarely starts.
And then there is the Wayne Rooney question.
Surprisingly, left out at Liverpool because he was apparently ‘not right’ after his Euro ban, he was subdued against City and is prone to fallow spells when his mind is troubled.
United will regroup, of course.
But Sir Alex will be concerned that City looked too powerful and good for them all over the pitch.
That 8-2 mauling of Arsenal seems a long time ago now.
Problems are surfacing and on Sunday it was their turn to take a pasting.
City, meanwhile, are looking like champions-elect – a perfect balance of silk and steel producing goals galore.
Some are even starting to warm to the wayward two-goal Mario Balotelli, whose ‘Why Always Me?’ t-shirt showed there is a sense of fun behind the scowl.
But it is the magical and balletic Silva who is taking top billing as the Premier League’s most dazzling talent.
Last year City were pragmatically effective.
Now the ugly ducklings are transformed into gliding graceful swans.
Roberto Mancini’s team should win this title.
The only question now is whether they have the nerve to last the course?