Indeed, that only deepens the discontent. How has the principle competitive rivalry of the Premier League era dissipated so abruptly?
The key word is obviously "competitive." Man United and Arsenal fans may still feel vestiges of the seething rivalry that has defined much of their Premier League experience, but there remains little or none of it on the pitch—or on the sidelines.
As Arsenal's power in the league has waned while United have held strong, the acrimonious relationship between managers Arsene Wenger and Alex Ferguson has mellowed considerably.
The days of captains Patrick Vieira and Roy Keane starting hostilities in the tunnel even before kickoff seem distant.
As Man United collect their 20th top-flight championship—with an amazing 13 coming under Ferguson's reign—their dominance looks virtually unassailable. Those numbers make any sort of competitive rivalry seem far-fetched.
Yet all sports fans know that dominance is cyclical. Even the strongest dynasties can fall as circumstances change. The balance of power in the Premier League is undergoing a major change in circumstance.
Arsenal's fall from league contention has precisely coincided with challenges mounted by rich patron-driven Chelsea and Manchester City. There are three major reasons United have managed to avoid falling by the wayside in a similar manner.
First, United still retain the top revenues in the Premier League, as shown by the league's financial reports summarised this April in the Guardian. This has enabled them to keep wages relatively high and hold on to key players just as Arsenal have seen theirs whittled away.
That largely contributes to their second strength in this period: a core continuity in the team, also helped by the remarkable longevity of one-club veterans like Ryan Giggs and Paul Scholes—players essentially of an earlier era.
Third, that continuity extends of course to the manager, who has maintained a distinct winning culture through a combination of keeping key players, the awe-inspiring success of his tenure and to some extent, sheer force of personality.
Apart from the massive revenues driven by Old Trafford's size and the club's global commercial popularity, all those factors are perishable. In famously hale financial health themselves, Arsenal are one of the few Premier League clubs in good position to thrive under Financial Fair Play, which, if strictly enforced, could give them the competitive edge in wages they have recently been on the wrong end of.
So the competitive gap looks likely to narrow.
At the same time, this season has seen a real shift in the character of the Arsenal side, one that hints at a grittier, more determined team—exactly the type of team that used to revel in the United rivalry.
Players like Aaron Ramsey and Jack Wilshere leave no doubt about their loyalties. Wenger appears to be recreating an Arsenal culture of pride that seemed precarious or even completely lost in the past two or three seasons.
Needing three points when the sides meet this weekend, Arsenal will be far less concerned with honouring United than beating them.
This match could mark the return of a beautiful rivalry.