Time waits for no man. It was not the argument Sir Alex Ferguson usually makes or even, perhaps, the one he intended to advocate. Nevertheless he said: "Nature catches you eventually in life."
He was discussing Edwin van der Sar's excellence against Arsenal. As Ferguson ruefully conceded, his goalkeeper is pushing 41, not coming up to 21.
The Dutchman, unlike his manager nine years ago, is unlikely to rethink his retirement. He will go out where he deserves to: at the top.
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• Manchester City set up derby clash with United for ideal FA Cup semi-final
• The Premier League's French connection
• Sevilla have lost their magic touch
• 'The Little Aeroplane' is really taking off at Roma
Which brings us to Ferguson. The Scot enters his eighth decade in December and, in the aftermath of his second Champions League win in 2008, said he would not be the Manchester United manager at 70.
He may be studying the examples of Raymond Goethals, who managed Marseille to European Cup glory when almost 72, and other active septuagenarians like Sir Bobby Robson and Giovanni Trapattoni.
It is not nature that Ferguson has to worry about, however, as much as Manchester City, Liverpool, Arsenal and Chelsea. A man with an intense dislike of second place would not want to bow out anywhere other than first.
Now he has the opportunity to do just that. Sunday's FA Cup draw offered a Manchester derby in the semi-final. And while United have not won the competition since 2004, City's rather longer wait is more likely to exercise Ferguson's mind.
Think of last season's Carling Cup: winning the trophy itself seemed of secondary importance to stopping City prosper. Ferguson fielded arguably a stronger side against the local rivals than he did in the final itself against Aston Villa. He has won so much he barely needed the Carling Cup. City did.
The parallels with this season are considerable. Should City be overcome at Wembley stadium in a month's time, a final against either Stoke City or Bolton Wanderers would be significant for two reasons: the chance to earn yet another trophy and the likelihood it would ensure a fourth double of Ferguson's reign (one of his many records that is unlikely to be surpassed).
Yet given the nature of relations in Manchester and the delight the manager takes in seeing his rivals fail, the greater pleasure may lie in extending City's wait.
Ferguson did not achieve all he has to exit as the manager of Manchester's second team. And while there is no inevitability to City's advancement, it is a probability nonetheless. With further investment, Roberto Mancini's side should be stronger next season.
Without it, United may not be.
Ferguson has been staving off decline brilliantly. Injuries and a wish to spare players for tonight's Champions League tie with Marseille dictated the choice of a distinctly unusual midfield against Arsenal on Saturday; by fielding the Da Silva twins on either wing, he managed to pull a couple of rabbits out of a hat.
The danger of such magical feats is that it convinces people, whether United's parsimonious owners or Ferguson himself, that he has an enduring ability to perform such tricks. Logic alone dictates that it is not possible.
Moreover, this summer might provide the culmination of a life's work. Unless a somewhat flaky Arsenal side rally, Ferguson will clinch his 12th league title and United's 19th, overhauling Liverpool's long-standing record of 18.
The notion of historical superiority should appeal to Ferguson. If it is augmented by the FA Cup, the fourth double would be all the more impressive because this is a weaker team than the sides of 1994, 1996 and 1999.
All of which would make it an appropriate time to take his leave, with United in the ascendant but the warning signs that their domination might not last much longer.
Ferguson's decision is complicated by his vast emotional investment in United and his reluctance to surrender the reins of power. This guess is he will linger on a little longer, but it might be a rare opportunity to fashion an ideal ending.
The first and best of the FA Cup quarter-finals was a tale of two substitutions. Owen Coyle sent on Bolton's eventual hero Lee Chung-yong with half an hour remaining.
Only seven minutes remained when Birmingham City's Alex McLeish traded in a defender, David Murphy, for another forward, Matt Derbyshire.
McLeish is often cautious, but this time he cited the SAS motto, "who dares, wins". On this occasion, daring brought defeat: the winger Jean Beausejour was relocated to left-back in the subsequent reshuffle, and he was outjumped by Kevin Davies to set up Lee for the injury-time decider.
As much as Avram Grant may moan about the refereeing decisions in West Ham United's defeat to Stoke, and predictable as his complaints were, credit is due to City's match winner.
Danny Higginbotham's free kick was struck beautifully, but also well thought out: when defensive walls jump as a matter of routine, it can be profitable to drill the ball underneath them.
Eliminated from three competitions in a fortnight, the one consolation for Arsenal should come from the fixture list.
After playing 10 games in the space of 35 days, their remaining 10 matches come in as many weeks. It should mean squad rotation is barely required in a concerted attempt to win the title.