After Jack Rodwell's header for the hosts had cancelled out Juan Mata's opener in the first half of the Barclays Premier League contest, Januzaj was brought on in the 63rd minute as a replacement for Darren Fletcher, simultaneous to Danny Welbeck coming on for Robin van Persie up front.
And the manager - who was without the likes of injured midfielders Michael Carrick, Marouane Fellaini and Ander Herrera - told reporters: "It is not usual that we have four injuries in midfield. Every club that has that has a problem.
"That is why I played Januzaj in midfield, (and) because as a coach I want to win. I have said that we need creative passing and I thought Januzaj could provide that. That is the reason."
United's next match is Tuesday night's Capital One Cup tie at MK Dons, and Herrera (ankle) will have his condition assessed ahead of the match.
Whether the Spaniard makes it or not, it certainly seems Van Gaal will not be experimenting by giving Kagawa a go in the holding midfield slot in the game after the damning assessment he made of the Japan international's previous effort.
The Dutchman said: "Kagawa, I have tried to play him in that position in the United States (in pre-season) and he could not fulfil my wishes and my philosophy. We have spoken about that and he is more of a 10.
"Juan Mata was playing at 10 and I thought I had to change the other players, which is why I chose to bring on Januzaj. It is because of creation. Kagawa can also create, but I asked Adnan to play there because of the lack of midfielders.
"When he played in Belgium, he played in midfield so I asked if he could do it for us. I said to him, 'You are on the bench as a midfielder,' because I want him to focus.
"He played there and you could see it's not so many times that he's played there. But he did his utmost and I cannot demand more."
Kagawa, an unused substitute both in Sunday's clash and United's campaign-opening 2-1 home defeat to Swansea the previous weekend, has been linked with a move away from Old Trafford and it will be interesting to observe what part, if any, he plays in the MK Dons fixture.
It is not expected that new signing Marcos Rojo's work permit situation will be resolved in time for him to make his debut in the tie and it remains to be seen whether fellow defender Rafael will be deemed fit enough to feature.
It is understood United are looking to have the British record signing of Real Madrid winger Angel di Maria wrapped up by Tuesday evening, although the expectation is that the deal will not be complete in time for him to be involved at Stadium MK.
- Sports & Recreation
- Shinji Kagawa
- Juan Mata
- Ander Herrera
- Danny Welbeck