This was relegation day for Arsenal. Manchester United were gleefully unsparing as they illustrated all the weaknesses in the ranks of the opposition who could no longer be taken as members of the elite. The visitors had players such as Thomas Vermaelen injured while Cesc Fábregas and Samir Nasri have been sold but that does not begin to account for a drubbing. Their display had descended into capitulation long before the close.

Distress was deeper still since this debacle came fast on the spirited victory away to Udinese in the Champions League. While United are a side of a different order to the Serie A club, it was extraordinary to witness an Arsenal line-up that could not protect itself in the second half. On the verge of the interval a Theo Walcott shot through the legs of the goalkeeper David de Gea had the visitors only 3-1 behind.

This, all the same, proved to be an Arsenal line-up without the faith in itself to mount a semblance of resistance. It was, of course, the most severe defeat of Arsène Wenger's 15 years with the club. Until now the talk had been of the need to make signings but a couple of arrivals in the next few days will scarcely suffice to restore the morale of supporters.

It will be difficult to persuade those fans that newcomers still on offer as the summer transfer period comes to an end will galvanise Arsenal. A title bid looked all but inconceivable and the first aim for the club should simply be to extend its run of Champions League appearances next season.

If they were unlucky at all, the misfortune was to be observed in the ravenous appetite for goals shared by United and their supporters. There was a type of compliment in that since it implied that Arsenal were still perceived as a club whose ranking was not really so distant from their own. That perception cannot survive among the Old Trafford crowd unless radical action is taken by Wenger.

He does have many injuries yet the manager would doubtless have argued beforehand that he had trust in his squad as a whole. At heart, of course, he will have appreciated how thin the means have become at the Emirates. Wenger would be justified in pointing to the excellence of the victors, although a paean to United will not soothe Arsenal fans.

For neutrals, though, it is essential to applaud what Ferguson has achieved in fairly recent days. Once more his defence was short of full strength but that calibre of stand-ins, if such they be, is impressive. A youngster such as Danny Welbeck opened the scoring here before picking up a hamstring injury.

If no mercy was shown to Arsenal it was not simply because United lusted for this rout of a fellow Champions League club. These are footballers who must be utterly sure they will be sidelined if they offer anything less to the club than every trace of ability they have within them. Arsenal, on the other hand, were eventually listless and confused. There was scarcely a basic structure to the side.

Carl Jenkinson escaped the scene but only by receiving a second caution when the score stood at 6-2. His team-mates might have envied him. It was, in particular, horrid for the teenager Francis Coquelin that he should make his Premier League debut on this day. All that remains for Arsenal is the notion that the action might have taken another direction.

Wenger's line-up inflicted pain on themselves when, with the score at 1-0 for United, De Gea dived to his right in the 27th minute and saved a penalty from Robin van Persie. It had been awarded following a Jonny Evans challenge on Theo Walcott. Within two minutes the lead was extended as Ashley Young bent a shot into the top-right corner.

The United opener had come when Anderson lifted a pass over the defence and Welbeck was too sharp for Johan Djourou as he headed home the bouncing ball from the edge of the six-yard box.

United's third, in the 41st minute, was bent into the top corner by Wayne Rooney after he had tapped a free-kick sideways to Young, who stopped it and left the forward with a better shooting angle.

Although Walcott trimmed the deficit on the verge of the interval, Arsenal could not really resist here. The second half was even more of a rout.

Further United goals followed with Rooney curling home an almost identical free-kick attempt to his first goal, Nani finishing stylishly from the Englishman's service, the substitute Park Ji-sung coming off the bench to strike and Rooney himself completing a hat-trick from the penalty spot after Walcott had pushed Patrice Evra.

In the midst of the barrage Van Persie had scored to reduce the deficit to 6-2. It was hardly the sort of resistance Arsenal had hoped to mount and the punishment was so relentless that Young struck an eighth goal for United in stoppage time, with another unstoppable curling shot into the top corner.