Age is not just a number, it's a footballing philosophy. Or it is for some, anyway. Youth can give a team a futuristic look. It can generate excitement in a way that experience does not. It can be a sign of progressive management. A tantalising taste of things to come.
From the Busby Babes to Fergie's Fledglings, some of the finest teams have been both raw and remarkable. Others have sprung to prominence by advertising potential that was never quite realised. David O'Leary's Leeds side, who he called "my babies" so often that others mockingly adopted it, reached a Champions League semi-final but did not win a trophy. Arsene Wenger's Arsenal teams have long seemed a year or two from delivering, to the extent that some believers lost faith.
Nevertheless, choosing the untried is often a sign of progressive management. Against West Bromwich Albion in the Capital One Cup, Liverpool fielded a side with an average age of 23.6, and even that was raised significantly by the presence of Jamie Carragher. In the subsequent two Premier League games, three teenagers - Andre Wisdom, Raheem Sterling and Suso - all started. The two wingers were chosen in preference to the more seasoned Joe Cole, who was on the bench against Stoke, and Stewart Downing, who was not even in the 18.
An experimental approach also provides an explanation for failure; it is defeat but with the promise that short-term pain will yield a long-term gain. This is why one of football's great divides is between youthful idealism and ageing pragmatism. Just as there are successful and unsuccessful, attacking and defensive, direct and short-passing teams, there are young and old sides.
They are created by managerial principles, transfer-market policies and clubs' individual situations. Liverpool and Arsenal are on the inexperienced side of the split. Chelsea, after the exodus of the elderly, may plan to join them, along with Tottenham, especially when Brad Friedel and William Gallas' status as first-teamers is revoked. The ageing are represented in particular by Stoke, QPR, Fulham and West Ham, albeit in very different ways. Straddling the great gulf are Manchester United, with the remaining fledglings, the pensionable pair of Ryan Giggs and Paul Scholes providing reminders that Sir Alex Ferguson values both the proven and the promising.
United's business is indicative of their approach. Since the 2008 signing of Dimitar Berbatov, a fee has only been paid for one player over 26: Robin van Persie, rare evidence of short-termism. Nor are they alone: their fingers burned by Downing, Liverpool opted not to pay £6 million for the 29-year-old Clint Dempsey. While Tottenham did, the sacking of Harry Redknapp, whose squads tended to be packed with ageing players, was a sign of a shift in their approach. As Berbatov, Michael Carrick and Luka Modric show, they have made plenty of profits on footballers whose careers were on an upward trajectory.
Resale value is now part of the equation. It is about the balance sheet as well as the scoresheet. Yet while it is logical that players at the peak of their powers cost most, the reluctance of many leading clubs to spend money on footballers in the second halves of their careers creates a vacuum.
It is an opportunity for clubs in the next tier. While his wages are high, the £4 million fee Fulham paid for Berbatov appears absurdly cheap for a player who top-scored in the Premier League in the 2010-11 season. Craven Cottage seems a retirement home: 13 months ago, seven players of 30-odd started the draw against Blackburn.
Some Stoke sides are little younger. Tony Pulis' method of establishing them in the Premier League has been to sign proven top-flight players, many of whom have the same clubs Liverpool, Spurs, Sunderland and Southampton on their CVs. Peter Crouch, a case in point, cost £10 million when 30: it is a reason why Stoke faced no competition from top-six clubs for his signature.
In other respects, Pulis has copied Sam Allardyce's blueprint. In a time when transfer prices were lower, the current West Ham manager was able to pack his Bolton team with veterans that European giants allowed to leave for cut-price fees, for free or on loan. Allardyce used sports science to extend careers, but he also illustrated his astuteness.
In contrast, there is QPR. Mark Hughes has a phalanx of Champions League winners - indeed, only Chelsea and United have more - without shaking off the impression that he has merely rounded up the familiar, paying excessive amounts for declining players with diminishing motivation.
But the Pulis-Allardyce approach shows the advantage of experience. It is a practical way of securing Premier League survival. Theirs are not clubs with the luxury of being able to plan long into the future, assured they will be in the division. As Allardyce pointed out, he could not spend £4 million on 18-year-old Nick Powell, as Ferguson did: he needs an immediate return on his investments.
Moreover, while West Ham is an exception among the older teams in having an excellent youth policy, Allardyce's pragmatic streak is invariably evident. The purchase of 29-year-old James Collins is a case in point: the Hammers are likely to lose money on the deal but the centre-back will probably help keep them up.
Meanwhile, Aston Villa, who sold the Wales international, are making a rapid transition from old to young as Paul Lambert casts aside the conservatism of the Alex McLeish era. Then the ingénues were only selected because of injuries. Now they are actually preferred.
The Midlanders are not being entirely original. Four years ago, Newcastle represented everything that is wrong with ageing teams. Scouting seemed concentrated on the rich and famous; vast sums were committed in fees and wages to players of decreasing financial and footballing value. Now they have rebranded themselves as flagbearers for the improving. They have identified the up and coming, often at bargain prices. That has long been Wenger's specialist subject although, while the Frenchman inherited an old side, it has only been in the latter years of his reign that Arsenal became a young team
Too young, perhaps. The signings of the last 14 months, including Mikel Arteta, Santi Cazorla and Lukas Podolski, seem an acceptance that youth needs to be diluted by experience. Even Fergie's Fledglings had the core of Peter Schmeichel, Gary Pallister, Denis Irwin, Roy Keane and Eric Cantona. The newcomers caught the eye but it was about getting a happy medium. A generation game was not won by one generation alone.