And yes, it does seem curious that he is once again fit while Wayne Rooney is injured. How convenient.
Rooney was poor against Swansea, despite his work rate, so it is very possible Sir Alex has given him a few days to get his body fit for 90 minutes.
The manager will have been encouraged by the partnership between Robin van Persie and Javier Hernandez on Wednesday and, with Kagawa needing game time, he gets the chance to play the Japanese man at the top of a diamond or in a 4-2-3-1 which could be the likely formation against West Brom.
Too much stereotyping
When looking at United's apparent needs in the transfer market or even in their match-day formation, there is too much stereotyping by supporters.
So they say Sir Alex should buy a defensive midfield, even though he has made clear United don't need one and that, with any tackle being punished, they are an anachronism.
That in no way denigrates the value of a tackle, but you will now see that defenders aren't tackled in the penalty box for fear that the opposition player will dive.
We saw this also with Chicharito against Newcastle. He tracked Sylvain Marveaux all the way to the edge of the penalty box and then let the Toon man go for fear of giving a penalty. The latter simply tapped his heel against the Mexican and got a free kick.
It is seriously worrying that players have been trained to dive and how to dive. How can a referee tell the difference between an accidental contact, a trip and a player who flicks his leg sideways into the defender's leg and goes down?
This and the whole debacle of handballs is causing a controversy that eventually will only be resolved if football introduces the same approach as rugby.
"Can I award a goal?" or "can I award a penalty?" could be resolved in 30 seconds. In addition, we should have a dodgy dives panel every Monday and every shirt pull should result in a penalty. The latter two problems would be resolved in a couple of weeks if such action was taken.
Because make no mistake, football's image is being badly damaged by the diving and cheating and rightly so.
Anyhow, rant over and to return to the matter of stereotyping.
United definitely need at least one new player in midfield and, to satisfy Sir Alex, it should be a "box to box" player like Kevin Strootman, not a DM like Victor Wanyama.
To turn it the other way round, people have asked how you can play Kagawa, who was a No. 10 for Dortmund, in the same team as Wayne Rooney, or Van Persie for that matter, in the role he was playing on Wednesday?
The implication is that Kagawa is inflexible, which he is not. Sir Alex would not have bought him if he was that inflexible, especially because United are now playing a "dynamic interchange" style, whatever format they apparently set up in.
That doesn't stop him fielding two "wingers" like Ashley Young and Antonio Valencia. Although Sir Alex would be unlikely to ever again sign such an obviously one-footed player as Valencia, the Ecuadorian does have good defensive qualities.
Young, on the other hand, is versatile. Nominally he plays on the left, but is just as comfortable on the right or indeed through the middle, where even for England he has played as a second striker or in the No. 10 role occasionally.
The secret to Kagawa is to use his technical skill and adaptability
Shinji Kagawa has excellent technical skill and foot speed that are similar to Lionel Messi. Nobody would say he was as good as the little genius, but Sir Alex turned Cristiano Ronaldo into a world-class player, so why not Shinji?
He may not be the best tackler but he makes up for that with phenomenal work rate, fitting the mould of the typical Dortmund player, chasing and harrying.
What is abundantly clear is that, being genuinely two-footed and intelligent, he could play as No. 10, at the top of a diamond, at the centre of the three in a 4-2-3-1, or on either wing.
If you look at a video of his skills and goals, he can beat a defender and centre from either flank, dribble through the middle and also score goals with either foot.
In terms of his skill set he is actually quite similar to Tom Cleverley, except that the latter is a better tackler. When you watch the difference Cleverley made after he came on against Newcastle, Kagawa can also do the pacy incisive runs, the flicks into feet, the quick one-twos.
Like Van Persie he can drift out to the wing to create space, and like Anderson he can run through defences.
You would not expect him to play beside Michael Carrick in a 4-4-2, or a 4-2-3-1, however.
How to best use him on his return
There are two sides to this. The first question is how to best use him if the whole squad is fit; the second is how to use him with the current injuries.
There is some defence for Sir Alex over his team selection on Wednesday, because he had Young, Nani, Rooney, Danny Welbeck and Kagawa unavailable. So it had something of the makings of a "scratch" team.
This didn't stop the inevitable questions yet again about giving younger players a chance rather than the one-paced Scholes.
Maybe it was too early for Ryan Tunnicliffe or Davide Petrucci, but Nick Powell was nowhere near the bench even. Surely he has done enough to get a start and can't possibly have done worse than Scholes?
There will still be some injury challenges tomorrow as well. West Brom were able to rest Peter Odemwingie and Shane Long against QPR, so one assumes they will return.
Sir Alex is a past master at keeping a trick or two up his sleeve. In his press conference as mentioned above, he indicated that Rooney would be out and Phil Jones would be assessed on the morning of the match.
Kagawa would probably make the bench, but it was not reasonable to expect Ryan Giggs or Paul Scholes to have recovered. According to the "Physio Room," Nani and Anderson are the only other players missing through injury.
So a possible starting line-up for tomorrow is:
Rafael, Vidic, Evans, Buttner
Young, Carrick, Cleverley, Welbeck
Lindegaard, Jones, Smalling, Fletcher, Powell, Tunnicliffe, Kagawa
On the other hand, if Kagawa has been training for almost a week, he could start behind Van Persie with Hernandez on the bench.
So that would apparently satisfy all those who think that is Kagawa's best position.
But what would Sir Alex do if everyone was fit?
If he played the diamond then the front six could be:
Rooney, Van Persie
And if it is a 4-2-3-1 the personnel could be:
Valencia, Kagawa, Rooney
And even with a 4-4-2 or 4-4-1-1 Sir Alex could use:
Young, Carrick, Cleverley, Rooney
Kagawa, Van Persie
...with the possibility of alternating Kagawa and Rooney.
But in any case, the coaching philosophy at United is now that pretty much anyone needs to be able to play anywhere, subject of course to the natural division between defence and attack.
So what are your thoughts?
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