So, Sir Alex has experimented with the so-called "diamond formation" and, although it produced a result against Newcastle, there are arguments for and against Manchester United using it.
Somewhat bizarrely, he appeared to suggest, as reported in The Guardian, that it's greatest value was in confusing opposition coaches!
"I think the level of the game in England and Europe is such a high level now that making yourself unpredictable is going to be a strength, Teams will have to think if we are going to play two wide players or the diamond because we have players capable of doing both things."
Now that is one smart move.
If any of you watched "Being Liverpool", you might have got an insight into how coaches think and work.
The very best of them analyse the forthcoming opposition, and school their team into how to play, including the tactical formation.
This seems to have been particularly hard for the Manchester City players to get a grip on.
When you've joined a club for £200,000 a week and you just want to go out and blitz the opposition, it must be quite frustrating to have to go back to school.
Zonal marking seems to be a step too far, judging by Tuesday's performance. Some of the players also seem uncomfortable with trying to play three at the back.
The thing is, when you have world class players with instinctive ability, do you really want them to be stood thinking "what should I be doing now?" rather than expressing themselves in a fluid formation.
4-4-2 works for United. 4-3-3 flexing to 4-5-1 works. And now it seems that 4-2-3-1 works as well.
It's mainly about getting the best out of the players you have. Of course there's an element of nullifying the opposition.
But United's tradition has been about out-and-out attacking football. Lesser teams may set up to counter this, but at a cost to their own attacking ambitions.
And two things have been key recently: the midfield being part of a tightly organised defence; and playing a much higher line on the pitch.
You will occasionally concede a breakaway goal like Michael Kightly's for Stoke, but in general the aim is for United to crush the opposition with goals, goals, goals.
So why use the diamond formation?
One thing that seems to have been missed is that when you have wingers injured, you need a Plan B. Of course you can play Rooney or Welbeck out wide left, for example.
Not only that, but the diamond, or 4-3-1-2 allows Sir Alex to use Cleverley and/or Anderson, as was clear in the Newcastle match.
So, given the manager's proclivity for using Carrick or Fletcher as a holding midfield, the most likely personnel would be: one of those at the base; Cleverley and Anderson at the points; and Rooney or Kagawa at the tip, with two strikers at the top.
So if Kagawa was at the tip, Rooney and Van Persie would play up top. That has already been shown to be a powerful partnership.
The idea of a diamond may well have been spawned out of the shambles in the first half against Tottenham. According to Sky Sports, United set up as a 4-5-1 in that period, but it looked more like a 4-2-3-1 at the time.
The problem was that Giggs was poor and the Carrick, Scholes combination has them both playing too deep. A vacuum opened in midfield that Bale and Vertonghen particularly were able to fill.
Once United moved towards more of a traditional 4-4-2 they were in with a real chance of winning.
But does the diamond work?
There seems to be some uncertainty in the manager's and the players' minds. This was best evidenced last night.
United appeared to set up as a diamond, and a very attacking one at that, but in practice it looked to the uneducated eye as if nobody was quite sure where they were supposed to be playing.
There is a lot to be said for having a fluid interchange in the front six, but last night at least three of the midfield seemed to be looking for a role.
United set up with an attacking diamond in the first match at home to Braga.
Yes, they gave away the first two goals, but with Fletcher at the base and Cleverley in front there was much more certainty. Also, Rooney, Van Persie and Hernandez were on from the start.
So last night, all the personnel changed, except Rooney.
Notionally he was at the top of the diamond, but because Anderson was driving or staying forward, Rooney kept dropping back into the base position and ended up far too deep to do enough damage.
Giggs didn't seem to understand what his role was and couldn't really be identified as playing anywhere in particular; and Nani was all over the place.
At least if he had stayed on the wing, swapping with Valencia and attacking a very vulnerable full back they might have achieved something.
So it looked pretty much a shambles until Rafael replaced Nani, Valencia moved forward, Van Persie came on and United reverted to a 4-4-2.
It's impossible to assert whether it was the formation change or the personnel change that led to the eventual comfortable victory.
The fact is that United won both legs against Braga by changing to 4-4-2 and looked vulnerable with the unfamiliar diamond.
The jury is still out
So in summary, it seems that United can make a diamond work against the right teams, with the right personnel. The ideal would be:
Carrick or Fletcher
Cleverley and Anderson
Rooney or Kagawa
And what does it achieve?
Most notably it can give control of central midfield, but this could be at the cost of losing control down the wings against a team playing wide players and overlapping wing backs.
Maybe Sir Alex has it in mind to use against top teams like Barcelona, but it is hard to see how that would work.
In addition, there seems to be too many risks attached if any of the players are uncertain where they ought to be.
This is a risk of any formation change that is unfamiliar. Manchester City looked all at sea for set pieces against Ajax, with nine players looking at each other in a zonal defence and wondering who was marking who.
Also, they clearly aren't comfortable yet playing three at the back. Barcelona can do this because they have done it for some time, but they were also undone by Celtic last night.
The conclusion would have to be that the diamond worked against Newcastle's 4-4-2 because Pardew had set up as if United were going to mirror that formation or play 4-3-3. The latter took the game by the scruff of the neck from the off; the Toon looked disjointed all night and United strolled to a win.
The diamond also seemed to work against Cluj, but in truth the latter set up to defend with nine back and one up. It was United's close passing and individual skill that broke them down, not a fancy formation.
So the granny from Rochdale was probably right. If United play a mediocre team who plays it narrow, they can dominate midfield and win at a canter if the players on the pitch are good enough.
Last night Giggs, Anderson, Welbeck and Nani had an off night. The diamond was never going to work. It took reverting to tradition to get the win they needed.
As we've said before, "if it ain't broke don't fix it".
Celtic showed last night that sheer determination, organisation, played to a high energy level can get a result. As many suspected, when you put the Barcelona defence under pressure it can crack.
Other teams have simply tried to stop Messi, but as Chelsea showed last season, if he has an off night Barcelona can be beaten.
If the diamond works for United it will probably be because the defensive organisation is perfect. There has been a significant improvement here as the last few weeks have shown.
As we've said elsewhere, the missing ingredient last night was Carrick or Fletcher at the base, rather than three different players wondering in turn if they should be there.
The conclusion on formation would therefore have to be: ditch the diamond and use 4-2-3-1 instead. Either that or use 4-4-2 with Valencia wide right and Young wide left and score more goals than the opposition.