Forget his work through the season, all those goals and assists, or simply as the point of attacking focus they sorely needed. Right now this question concerns only Monday night and how anti-climatic United's Premier League title-sealing win over Aston Villa would have been if not for Van Persie's hat-trick, and specifically the second goal.
Maybe it was not the goal of the century his manager thought, but it was brilliant, evoking memories of the wonderful goal Zinedine Zidane once scored for Real Madrid, volleying home from more of an angle an equally wondrous diagonal ball from David Beckham.
But had it not been for the Dutchman, this title might have felt a bit of a damp consolation, not just for the margins by which it was won, but for another season without a European title.
Which is scandalous because that would numb the monstrous scale of the hegemony United have established in England since 1992/93. A 13th title in 21 seasons means that the right question to ask tomorrow, the day after and forever and a day after that, is where would United be without Sir Alex Ferguson?
With each title triumph, it becomes easier to under-appreciate how successful he has made United. The full impact of it will only become apparent years from now. For now, to capture a sense of it, it might be worth looking outside the triumphs, at the details of non-triumph in fact.
Details that say, for example, that United have not finished once outside the top three in England's top division since 1990/91 and that they have finished runners-up five times; when they are not winning titles that is, they are doing an exemplary job of refusing to give them up without an almighty fight.
No team across the three other main European leagues in Spain, Italy and Germany matches that. Bayern Munich come close, having won 11 league titles in the same period and finished runners-up six times. But they have had a couple of clearly poor seasons, finishing sixth and fourth once.
Barcelona? They will have won 10 titles in 21 seasons when formalities are complete this year and their European triumphs place them highly. But they have also had seasons where they have not been in the running at all at home, finishing outside the top three four times in that period. The home successes of Juventus and AC and Inter Milan do not come close.
So back to Ferguson and wondering whether such a tenure can ever be replicated again in any sport and as a related query, whether a period such as these last 20 years will ever come about again.
Sport today has more of almost everything: money, ambition, competition, skills, science, knowledge, talent. But, crucially, it has shorter careers and far less patience. These days, ambitions are to create projects, not self-perpetuating empires.
United's era is a current, ongoing fact and yet it feels already as if it might have been compiled in a different time. It is so celebrated and accomplished that already this club should be in discussions about the greatest, most successful and longest-lasting sporting dynasties, whether that includes cricket's West Indies from the mid-70s to the early 90s, or the Boston Celtics and their 11 NBA championships between 1957/69.
And it is not over yet, which means, theoretically, that it is not only likely to be the last of its kind, but also the most immense of them all. It is constantly reinvigorating and regenerating itself, taking each season without a significant title as a personal slight and affront against its own history and existence.
In that time, entire squads have come and gone, though one central idea of the way United should play, a loose guiding philosophy, has remained.
Great players have come and gone, too, replaced by newer ones, hungrier than their predecessors to win. Van Persie being an excellent case in point.
Behind it is this man of unending motivation. Every season, Ferguson has found new desires to satisfy, ideas to implement, players to nurture, slights to be avenged. He has transplanted his own motivations onto that of an entire behemoth of a club, which is perhaps his and the club's greatest achievement.
Van Persie's goal was magnificent but it was hardly needed, either as exclamation to this season, or as a comma to an era.
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