In retrospect, it was a turning point. While Arsenal have struggled to maintain that form, United have gone eight games unbeaten - winning six and scoring 28 goals in the process. The catalyst has been two partnerships formed in the wake of the Highbury defeat. Gary Neville and Jaap Stam were immediately paired in defence and, a couple of matches later, Andy Cole linked with Dwight Yorke in attack. The decisions owed something to luck, in that they were partly prompted by injuries and the poor form of alternatives, but Alex Ferguson, a firm believer in partnerships, had found a couple of good ones.
The result has been a tighter and more constructive defence, albeit with room for improvement, and a livewire attack where Cole and Yorke's quick feet and minds have wreaked havoc. Cole has six goals in six matches since his recall and Yorke six in seven, and many assists.
"Yorke is so difficult to defend against," Ebbe Skovdahl said after his Brondby team had lost 5-0 at Old Trafford. "He seems to comes from midfield and creates more space for others. He is an annoying player."
The Tobagan is, in many respects, a quicker Teddy Sheringham. He may not have his range of passing but, with David Beckham in the side, that is not crucial. What he has is speed, of thought and movement. As United's second goal, created by a Cole dummy and Yorke pass, illustrated, the pair have quickly become attuned.
This has brought the best from Cole, who failed to strike up satisfactory partnerships with either Eric Cantona or Sheringham. Now, as he doubtless hopes to show his former club at Old Trafford on Sunday, he has the same confidence in front of goal that he possessed when in tandem with Peter Beardsley at Newcastle United.
"That second goal [which ended with Cole chipping in from a acute angle] was Cole's best finish," his manager, Ferguson, said. "He waited for the goalkeeper: that patience only comes when a striker is on form."
Cole and Yorke must now pit themselves against Barcelona on 25 November as United seek to erase the memory of their 4-0 drubbing in the Nou Camp four years ago and move closer to the knock-out stages of this season's Champions' League.
United's cause will be helped by the absence, from the Barcelona side, of Philip Cocu. The versatile Dutch international was booked for the second time in the competition on Wednesday and is suspended. Looking further ahead, Bayern Munich may also be understrength when they come to Old Trafford for the probable Group D decider on 9 December. This is because eight of their squad will go into their tie against Brondby carrying a yellow card.
United, incidentally, have two players on a yellow card, Jordi Cruyff and Sheringham. On current form this will not be a problem. Neither are likely to play.