Earlier this week he revealed that "alternating is not a problem for me. That's the policy I have been adopting and I'm comfortable with it" (via Football365).
Rotation may be a good concept in theory for Sir Alex, but in reality, surely all it does is diminish the confidence of both players.
If, like against Galatasaray on Wednesday, de Gea has a real barnstormer, keeping his team in the game with acrobatic saves, he is then dropped for the next game—is that really going to help his mindset?
The same goes for Anders Lindegaard, who is yet to concede a goal at Old Trafford in his United career.
De Gea may be the fashionable choice out of the two, but Lindegaard has shown a steady assurance in between the sticks that prevents him from making the kind of erratic mistakes such as de Gea's against Fulham a few weeks back.
The difference in the players' price tags, at least for now, doesn't appear to be as important a factor in Sir Alex's mind as some would make out.
The £3.5 million paid for Lindegaard is already looking like a bargain, whilst the £17 million paid for de Gea has yet to show real dividends.
That's not to say that the latter isn't the Red Devils' No. 1 option going forward, he is...most definitely.
The weaknesses in the 21-year-old's game will need to be ironed out first, but he is certainly made of the right stuff to become one of the top keepers in Europe for years to come.
Lindegaard on the other hand is 28 years of age, and nearing his peak as a player.
So why then the fuss? If there's little to split the two, why does the better long-term option not have the edge?
Sir Alex does not trust David de Gea yet, in the same way that he would trust Peter Schmeichel or Edwin van der Sar, even after either made a game-changing mistake as they periodically did.
You can talk all you want about the Stoke Citys and the West Hams of the league—bruisers who are likely to give a 6'4" keeper who's all skin and bone a torrid time of it.
But De Gea's most recent error that resulted in a Nemanja Vidic own goal wasn't a result of his being bullied in his own area, it was just poor decision-making.
Granted, he had a cracking second half of last season, and one could make the legitimate point that his performances alone should have seen him made the automatic No. 1 for this campaign too.
But such is Sir Alex's lack of trust in the young keeper; he makes one costly error and he's straight out of the team for the next game.
A player like de Gea is never going to improve his basics if he's not playing week-in, week-out.
The one game on, one game off rotation schedule just does not work for the young Spaniard. It may for Lindegaard, but not for de Gea.
If he's only kept for Champions League games and the less physical Premier League matches, he's never going to learn how to play the Stoke Citys and West Hams.
This impatience on Sir Alex's part seems to be just another consequence of his rabid desire to win it all in his last season or two, a ruthless impatience that saw him pay £24 million for a 29-year-old.
But David de Gea must be Manchester United's No. 1 keeper—it's that simple.
If United aren't going to put their faith in him now, they risk damaging the confidence of one of their young jewels, perhaps permanently.
Anders Lindegaard may feel hard done by, and rightly so. But his relegation to the bench would be a necessary evil.
There may not be room for mistakes at Old Trafford, but in David de Gea's case, the potential rewards far outweigh the price.
What do you think? Who should be United's No. 1 choice in goal?