Sir Alex has been flirting with new tactical formations this season, primarily for four main reasons:
To take account of the new "modern football" formations played even by teams like Swansea City, let alone Chelsea;
To keep the opposition guessing;
To counteract the blanket defence of lower teams;
To find a way to integrate Robin Van Persie, Wayne Rooney and Shinji Kagawa in the same team.
In the past, particularly in Europe, he has tended to use either the traditional Manchester United attacking 4-4-2 formation with two wide players or 4-3-3/4-5-1.
On Sunday his team is likely to be confronted by Chelsea playing a 4-2-3-1 formation, although this isn't necessarily so. Against Arsenal (who fronted up a 4-4-2), Chelsea started with a 4-5-1, but this is readily adaptable to 4-2-3-1 with the same personnel.
The two managers can only second-guess up to a point. Both Roberto Di Matteo and Alex Ferguson will be missing at least one key player.
While there is no certainty that Frank Lampard would have started, he doesn't seem likely to be fit in time. The biggest miss could be captain John Terry, presumably replaced by Gary Cahill.
Sir Alex already knows he will be without Shinji Kagawa, who picked up a knee injury against Braga and went off at halftime. Ironically, this makes his selection much easier, as he has shown an unsurprising proclivity to pick Robin Van Persie and Rooney together, ever since Wayne was fully fit.
Judging by the stats so far, that is hardly surprising: In the first three matches they started together, they shared eight goals and five assists!
In the past, Sir Alex has shown a tendency to match up his own formation with the opposition. There is every good reason to do this after a near disastrous experiment against Braga, where he decided to try the new "diamond" formation and had to abandon it at halftime.
Chelsea's team is fairly predictable:
Ivanovich Luiz Cahill Cole
Oscar Hazard Mata
If Sir Alex has learned anything from the Tottenham defeat and the first half against Stoke, he will surely let logic override sentimentality and not play Paul Scholes from the start. One of the reasons why is because of the threat of the pace of Mata and Hazard.
United start far too slow when Scholes plays alongside Carrick because Paul plays too deep. Against Spurs, this left a vacuum between these two and the front players, which Bale particularly was able to exploit.
Scholes is also not gifted with the ability to tackle. Both Hazard and Mata love to run directly at players. If they do that against the "Ginger Prince," he could be off for two yellow cards.
So United need pace, both to match the threat from Chelsea's midfield and to exploit the weakness inherent in their defence. Luiz takes too many risks, Ashley Cole's legs have gone, Cahill can be turned and Ivanovic can be exposed.
Although harder to predict, a possible United lineup could be:
Rafael Ferdinand Evans Evra
Carrick Anderson or Cleverley
Valencia Rooney Young
This formation allows the team to oscillate between 4-2-3-1 and 4-4-2 as necessary. Valencia and Young also have sound defensive qualities, as does Rooney, and even Van Persie can put in a shift as needed.
So how can United counteract the threat of Mata and Hazard?
The first and best way is to starve them of the ball. United must start with their patient possession game. This is where Carrick is key, but also, the pace and interchangeability of the players beside and ahead of him.
Ashley Young has pace, can play wide and also through the middle in the role Kagawa has played. Rooney and Van Persie have already shown that they are happy to wander out to the wings to stretch a defence and then ping crosses in. This may be even more valuable when Welbeck comes on in the second half.
Valencia is less flexible because he's so one-footed, but his pace and willingness to cross from the by-line are to be feared.
So, the second point is that attack is the best form of defence.
Jon Obi-Mikel is not having a stellar season and is not in the same league as Essien or Makalele before him. That means that Ramires can also be tied up deeper than he would like.
Hazard is not particularly useful in defence; nor is Torres, except at set-pieces, because of his height. Mata is willing to help out, but that would work in United's favour.
The danger comes when either is running through midfield with the ball. Hazard particularly has pace and skill and likes to run directly at the defence. Michael Kightly's goal for Stoke on Saturday showed that Ferdinand particularly can be vulnerable to this.
United's defence is key
The midfield, and especially Wayne Rooney helping out, can only do so much to stifle the supply and limit the runs of Hazard and Mata. Like the United attack, these two have an unlimited licence to play where they wish.
The key could well lie with the fullbacks. United have been unusually vulnerable to an early goal this season, having conceded first in eight of their 12 matches so far this season. It also happened in preseason.
Sir Alex can give the impression that he is bemused by this, but it is for him and his senior players to work out, because if Chelsea score first, it could be a long road back. United may have their best attack for years, but the Tottenham match showed they can't keep relying on overhauling a deficit.
The aberration against Braga can be put down to an astonishingly naive team selection by Sir Alex. Either he hadn't studied Braga (who had 45 attempts in their loss to Cluj), or he underestimated them.
As soon as their manager saw Carrick at centre back, he probably told his team to go on all-out attack. Not surprisingly, it was successful. Carrick was uncertain in his positioning, and Evans was asleep yet again. United were suddenly 2-0 down without threatening the Braga goal.
So you can confidently expect that United's only two fit central defenders, Ferdinand and Evans, will be on duty on Sunday.
The big step change made after the Tottenham debacle has been the fullbacks staying closer to central defence and only one being allowed up at a time.
Evra has not had a great season so far, and he keeps getting caught up-field. He has seen Wayne Rooney picked as captain against Braga and Darren Fletcher in the Capital One Cup. He must be feeling the pressure after Buttner also played well this week.
So he must show his sense of responsibility against Chelsea. There hasn't been enough leadership on the field in the absence of Vidic. Hazard, Oscar and Mata have the capacity to run the United defence ragged if it is disorganised.
Rafael, on the other hand, has really matured this season. Combining with Ferdinand and Valencia on the right, he can be relied on to stifle the runs down that flank. Torres is in poor form, so except at set pieces, there are unlikely to be many aerial crosses.
As they have shown against other teams so far, Hazard and Mata will look to penetrate United through skilfil ball play and interchange, so it is the rigid discipline of the defence that will be fundamental.
The choice of goalkeeper is straightforward as well. Irrespective of the fact that Lindegaard "spelled" his finger last week in training, De Gea has to start. Chelsea will pose less of an aerial threat, especially without John Terry. United need a world-class shot-stopper to deal with what Mata, Hazard and especially Oscar can throw at them.
Although Chelsea are having their best start ever, other teams have shown that Hazard can be managed. Oscar is still raw in some respects, and Mata can't do it all on his own.
United don't man-mark, but Anderson or Cleverley playing alongside Carrick could be crucial. Few players are better at interceptions than Carrick, but a pacy energetic midfielder is fundamental. He doesn't have to tackle so much as disrupt and prevent supply coming through.
It is dangerous to dismiss a £50m striker in "Nando," but he seems to be low on confidence and gets easily frustrated. Stop Hazard, and especially Mata, and you stop the supply to Torres.
With no Lampard to bring on and only a second-rate striker in Sturridge, if United can keep a clean sheet in the first half, they can lay the foundations of a win.
If they let Mata and Hazard do their stuff, their recent defensive frailty could see them struggling even to get a point.
Attack is the best form of defence. If Chelsea let United take the game by the scruff of the neck early on and build wave after wave of attacks, Rooney and Van Persie have the talent to carve out a comfortable win, as they did against Newcastle, negating any concerns about Mata, Hazard or anyone else.
Predicted Result: Chelsea 2 United 3 with Rooney, Van Persie and Welbeck scoring.
What do you think?