The photograph of a near septuagenarian who suddenly feels old.
The City hammering was hard to take; the Crystal Palace match was a shambles; the two matches against Basel and the home match against Benfica were a wake-up call.
If Sir Alex was ever going to call time, it was after the shambolic ECL exit. The Europa League will be a humbling experience, even if United win it. Those aren't the 'European nights' Sir Alex lives for.
He is, as ever, pragmatic, however. You can be very sure that the likes of Paul Pogba will get more chances in Europe than they otherwise would have.
Complacency and tactical naivety
There is no doubt that Sir Alex will have warned against complacency when United were given, in many people's opinions, the easiest Group in the Champions League.
Somehow, that didn't translate when United played Basel or Benfica. 2-0 up, against the former at home, they then imploded through extravagant enterprise. As against City, with Vidic absent, Evra could not fill the captaincy vacuum. He led his troops over the top in a cavalier charge and they got humbled.
The manager talked endlessly about being "too open," but how can he blame his players when he is on the touchline and in the dressing room. Maybe after the 8-2 hammering of Arsenal he was sucked into believing Shankly's mantra: "if we score one goal more than them we win." However, the opposition was much thinner on the ground in the 70s.
Irrespective of the injury troubles, which have been almost unprecedented, there have been tactical questions this season. But in the Champions League Final, Sir Alex and his backroom boys showed they had learned nothing since Barcelona beat them last time.
Once again. poor Michael Carrick was shouldered with the role of holding midfielder and the blame, after he was unable to cope with Xavi, Iniesta and Messi all at the same time.
Once again, the European nights master-plan was wheeled out - contain and counter-attack; and once again United were found out as tactically naive. Whether or not Barcelona are the greatest team ever, the match need not have been so one-sided.
The need for a tactical revolution
The United tradition is one of playing attacking football and going out to win every game. As Sir Alex has aged, he has slipped into a European rut of 4-5-1 which, despite the fitness and energy of his squad has now been found out too often.
The irony is that the tactical changes United need will work in Europe and the Premier League and they will fit with the tradition of attacking play and United's evolving squad.
The way forward is surely 3-1-4-2, modified to 3-1-5-1 as appropriate?
Barcelona have no centre-forwards; they simply have a load of players with skill and artistry in abundance who can score goals. They don't belt corners and set-pieces into the penalty area for tall strikers to head home. They play football on the ground, where Bill Shankly said it was meant to be played "that's why it's called foot-ball".
The new "centre back" will need to be first and foremost a footballer, with tackling skills of course, but with mobility, passing as well as heading ability and a willingness to go forward as appropriate. Ferdinand fits the model, but so do Jones, Smalling, Evans and many of the young centre backs coming through. They also play with more space between them.
You then no longer have full backs or wing backs. You have wide players with great ball skill and passing ability and defensive capability. The Da Silva twins, Fryers, Nani and Valencia fit this mould.
You have a holding midfielder who doubles as a "libero." Jones could play that role but so can Gaitan when he comes.
In the centre of the field, in the engine room, you have Xavi and Iniesta equivalents. Creative, attacking midfielders with skill, artistry and goalscoring capability in abundance. Cleverley, Rooney, Pogba and Morrison may qualify.
And up front, you have natural born goalscorers, again with ball skills, able to create goals out of nothing, but also able to sit on the shoulder of the last defender like Owen or Hernandez. At least one should have height as well as skill, to act as target man. Welbeck and Will Keane qualify.
Finally, everybody must have pace and upper-body strength.
Three at the back is the way forward. That's the way Barcelona play. United are developing the players and the squad to play this way. All they need is Guardiola to succeed Sir Alex.