The 19-year-old came off the bench against QPR on Sunday and little more than 24 hours later was playing against Sunderland Under-21s in a 4-0 win.
The Belgian winger hopes his determination even for the youth teams will impress United manager van Gaal.
Januzaj told MUTV: "Of course, I played a lot of games last season and I'm trying to impress the manager once again and get games again this year as well.
"I tried to do my best
Obviously, even if it's reserves level, I always have to show myself and improve
I got a hat-trick but I think I worked hard defensively as well and these are the kind of things I have to do now and at first-team level.
"I don't do it for any other people but for myself
I look after my [performance]
Even if I have to play under-18s, I have to do it and try to improve every time I play."
Source : PA
Source: PA