For years, the future has been a thorny topic at Chelsea.
It has been simultaneously debated and avoided, the outside world wondering when, and how, Stamford Bridge's greatest generation would be consigned to the past and the various managers pondering change and, in most cases, deciding it was too dangerous.
The future has arrived, suddenly, and Chelsea look particularly unprepared for it. This was not what they envisaged when Andre Villas-Boas was appointed with a remit to modernise. The brave new dawn has not materialised, nor the orderly transition from old to young.
Instead, they find themselves thrust into a different era, arriving by accident rather than careful planning.
The Chelsea pensioners are a diminishing band.
Didier Drogba is absent in Africa, representing Ivory Coast. Nicolas Anelka is languishing in China, allowed to leave after being exiled by Villas-Boas. Ashley Cole is banned, suspended for rash tackling at Swansea. John Terry is injured, and not merely with his pride bruised by the loss of the England captaincy. Frank Lampard's calf strain could sideline him, too.
It means that Petr Cech is alone among the 2008 Champions League finalists in being guaranteed to start. Even if Lampard, Florent Malouda and the recovering Michael Essien join him in the side, old Chelsea will be outnumbered by new.
This is the side Villas-Boas has been appointed to construct. Yet if his ethos, one of high-intensity passing and pressing, of building a pacey, progressive side, is an ambitious approach, this season has provided proof it cannot be realised overnight.
Delivering it with men from the margins of the side is still harder, let alone against Manchester United. A reliance upon the old guard has been especially apparent in the marquee games this season. After indulging their addiction to the aged, Chelsea enter generational detox on Sunday.
So this serves as an examination not only of the manager, but of all of the many power brokers responsible for assembling the squad.
Because the group who could execute Jose Mourinho's plan on autopilot are almost all missing, the organisational and motivational skills of Villas-Boas come into focus. The spotlight falls on inexperienced manager and untried players alike.
The successors are under scrutiny. Ryan Bertrand is Cole's understudy but has never been given a league start. More surprisingly, though with a shorter Chelsea career, neither has Gary Cahill, the January signing from Bolton Wanderers.
Villas-Boas has seemed strangely reluctant to pick the new signing; with two England defenders ruled out, can he afford to leave a third on the bench? Then there is a third prominent player who, for different reasons, has a question mark against his name.
Fernando Torres has gone 17 games and more than 1,000 minutes without a goal.
Drogba's departure to Africa offered the Spaniard on opportunity to impress. Instead, his plight has deepened.
Now he is offered a reminder of his greatest embarrassment as a Chelsea player: when Villas-Boas' side visited Old Trafford in September, the £50 million (Dh285m) man missed an open goal in particularly excruciating fashion.
The struggling spearhead can mask the accomplishments of others. Juan Mata, Daniel Sturridge and Oriol Romeu are the next-generation trio who have enabled Villas-Boas to reshape his side. Each has offered encouragement but thus far the rebuilding job has entailed taking a step backwards, in the hope that two forwards follow.
The contrast is supplied by their visitors.
United's has been a season of weakened teams, of random blends of aged and youthful players, yet they may end the campaign as champions.
It seemed their swansong when Ryan Giggs and Paul Scholes faced Chelsea in Moscow in 2008. Instead, United's old-timers are back for an encore, even as their Chelsea counterparts have, albeit temporarily, left the stage.