With Paul Scholes retiring, the inevitable question for several seasons now has been who can replace him?
The world is still largely agreed that United need at least one more midfielder.
United have some talented young players coming through, especially Nick Powell, Adnan Januzaj, Andreas Pereira and Ben Pearson. Freddie Veseli has looked impressive for the Under 21s in a holding midfield role.
The problem for Sir Alex is that while Veseli is 20, none of the others is over 18.
Powell is the most impressive and will surely get his chance as soon as United wrap up the Premier League. But the dilemma is best illustrated by the case of Paul Pogba.
Pogba was apparently frustrated that he wasn't getting more chances in the first team. He was 19 when he left for Juventus, where he is now an established member of the first team squad and has just been called up for the full French squad.
Of course you only want players who want to play for the shirt and stay, but when a bright young star looks at Wayne Rooney or Ryan Giggs who got their chances at 16 and 17 respectively, you can't really blame them.
Two things are clear, however.
First, the United squad will always be a blend of experienced and younger players. While people get frustrated with Danny Welbeck for example, he is still barely 22 and learning his trade. You could even say that his performance in the two ties against Real Madrid was "precocious."
Second, with Scholes likely to retire and Anderson surely surplus to requirements, Sir Alex could afford to make one or even two new signings in this area.
Much will hinge on whether he finally decides to move Rooney into midfield.
If they can get Robert Lewandowski and assuming that Chicharito stays, then Rooney could drop back into midfield for the rest of his career at United.
If Sir Alex was able to sign two of his targets, say Luka Modric and Kevin Strootman, then Rooney can stay up front.
What Modric or Eriksen and Strootman or Wanyama would give the manager is the flexibility to cover off all midfield possibilities:
Two attacking midfield (from Cleverley and Modric or Eriksen).
One holding and one attacking (say Carrick or Strootman and Modric or Cleverley).
One defensive and one attacking (say Strootman or Wanyama and Modric or Cleverley).
Two holding (say Strootman and Carrick).
After all, Sir Alex has managed to rotate five centre-backs successfully (Vidic, Ferdinand, Evans, Smalling and Jones). So why not five midfielders (say Carrick, Cleverley, Modric, Strootman and Powell)
But for the time being Michael Carrick can remain "pivotal" whether or not new players are signed or young players come through. He has, for example, formed a very effective partnership with Tom Cleverley, which at the moment is United's first choice midfield combination.
That is until somebody else is signed.
So with supporters clamouring for a new midfielder and the media having identified this as a potential weakness, you can be sure there will be at least one signing this summer, depending on who is available and who gets shipped out.
That will not phase Carrick.
He has come through the post Roy Keane era and all the criticism that followed, especially around the first Champions League Final against Barcelona, where he could hardly be solely blamed.
He has experienced periods where he lost his confidence and occasionally his form. But the manager has never lost faith in him.
When he was signed from Spurs he was not what many fans were looking for. But he has surmounted all those challenges and is now a "hero."
Robin Van Persie has been identified by all and sundry as the difference that has led to United running away with the Premier League. But you cannot ignore the massive contribution from their quietly spoken, unassuming, utterly professional "Rolls Royce" midfielder.
If Scholes' return from retirement was the pivotal factor that nearly won United a 20th title last season then surely, and especially in Scholes' absence, there is a case for Michael Carrick this season and beyond?