As befits a proud son of Govan, Sir Alex Ferguson has a tendency to wield the axe with all the subtlety of a Glaswegian kiss.
Even Beckham, Roy Keane and Jaap Stam, others ruthlessly discarded by Ferguson, were not dropped for cup finals (Bryan Robson and Steve Bruce were but, in the twilight of distinguished careers, sentimentality would have been a major reason in the selection of either).
Ferguson himself was similarly treated in his playing days and said as much when preferring Louis Saha to his top scorer at the Millennium Stadium.
But as is often the case, the Scot's argument hardly stands up to scrutiny. He stormed out, whereas van Nistelrooy duly took his place on the bench and collected his medal, though remained a study in distancing oneself from the proceedings.
Ferguson had footballing grounds for fielding Saha; his inclusion also acted as reassurance to the Frenchman about his future.
So often the bridesmaid for the biggest games, Saha had finally displaced one of the untouchables in the United attack.
Moreover, as the leading scorer in the Carling Cup, his selection was an act of loyalty from Ferguson. It was vindicated when Saha scored in the 4-0 win over Wigan.
And, quicker and more mobile than van Nistelrooy, he is also genuinely two-footed and possesses a wonderful natural spring.
With seven goals in his last nine starts, he is arguably the form forward at Old Trafford.
He certainly looks a more credible choice as a United player than at any stage since the weeks that followed his transfer from Fulham. And Wayne Rooney, with four goals in his last three games, appears the beneficiary of partnering Saha.
So a simple footballing decision? Hardly. There was a vindictive element in Ferguson's decision to ignore his top scorer and introduce Kieran Richardson, Nemanja Vidic and Patrice Evra as substitutes at Cardiff.
His subsequent omission can be presented as a consequence of the football truism about changing a winning team, but there is an unlikely air of permanence about Van Nistelrooy's station on the bench.
Three successive matches outside the starting 11 is hardly the definition of squad rotation.
But the prime cause of defeat, which was again apparent in the fortunate Premiership victory over Wigan, was United's powder-puff midfield.
Van Nistelrooy emerged from the dugout in a damage limitation exercise at the JJB Stadium.
Further evidence of what United were lacking was, inadvertently, supplied by his team-mates on Sunday. Newcastle were beaten 2-0, a thrashing in all but the scoreline. Saha was chief among the culprits in a display of profligacy.
And, unlike the French forward, van Nistelrooy may be a one-dimensional player, but his gift is the most prized in football.
Indeed, the best out-and-out goalscorer in the Premiership is exactly the sort of player Liverpool and Chelsea, whose European exits were in part a consequence of missed chances, require.
The timing of the ruptured relations at Old Trafford is intriguing; will envious glances be followed by concrete declarations of interest in the sidelined scorer?
Because van Nistelrooy's record is exceptional. He has 148 goals in 210 games since leaving PSV Eindhoven five years ago. For much of that time, he has operated without a strike partner.
He is single-minded enough to prosper as a lone striker; indeed, selfishness is a trait of many great strikers.
Van Nistelrooy, it has long been hinted, would not top any popularity contests at Old Trafford, but his appreciation for Rooney's chipped opener against Newcastle was generous and hardly the actions of a sulking predator.
His current status is a reminder of the capriciousness of football.
It is a matter of months since he figured on the shortlist to replace Roy Keane as captain and only a year since a semi-fit van Nistelrooy was rushed back to face Milan, United's fortunes seemingly dependent upon his return. Nostalgia is evident, too, in most interviews he has given, but he harks back to his first two seasons at Old Trafford.
Gorging himself on Beckham's crossing, he struck 80 times in two years. The Dutchman has never been that prolific since and even the England captain's best man, Gary Neville, makes reference to his departure less than van Nistelrooy; indeed, only the Old Trafford marketing department misses him as much.
With the more erratic Cristiano Ronaldo - not to mention whoever Ferguson perms from Darren Fletcher, Ji-Sung Park and Kieran Richardson - on the flanks, van Nistelrooy's supply line has deteriorated.
His admiration is unconfined, too, for another in exile. Roy Keane's comments have been endorsed by van Nistelrooy, in itself a veiled criticism of his team-mates. It continues the Dutch tradition of independent thought; Ferguson, however, rarely brooks dissent.
It is telling that Saha, despite his Carling Cup goals, has only struck three times in the Premiership; odds on a recall for United's top scorer against West Brom should be shortening.
His continued omission, however, is evidence that age has not withered Ferguson's fondness for a battle. To the bemusement of everyone else, he has picked a fight with van Nistelrooy.
The precedents, as Beckham, Stam and Paul Ince can testify, involve a high-profile sale, and not a change of management. This relationship may not be irretrievable, but the trial separation has revealed cracks.
And given the premium football rightly attaches to goalscorers - not to mention the wealthy clubs targeting a striker of van Nistelrooy's calibre - Ferguson may need his benched forward more than the Dutchman needs Manchester United now.