The 22-year-old rose to prominence at Old Trafford under David Moyes, scoring twice on his full Premier League debut in 2013 and being deemed one of Europe's brightest youngsters.
However, Januzaj fell out of favour at United and, four years on, the Belgian finds himself with Spanish side Real Sociedad, having been sold by Jose Mourinho in the summer.
Januzaj has largely attributed his stunted progress to Van Gaal's arrival in 2014, implying that Dutchman shackled the 20-time English champions and strangled his enjoyment of the game.
"There was not the same freedom," Januzaj told the Daily Mail. "A winger needs that confidence, a manager telling you, 'Go and take people on'. With him, it was a slow passing game.
"For some it was difficult. You could see some players were not enjoying the football. The manager and I had many difficult meetings. I was frustrated and everyone could see that I was not the same Adnan as the first year. I was sometimes even in the stands. When you work hard in training and then get left out, it's hard for a young guy.
"As a footballer, if you think too much on the pitch, it is never good. You need instinct in your play. When the ball came to us, we had to stop and think, "What are we going to do with it here?", 'I can't lose the ball'."
Van Gaal was sacked by United in the summer of 2016 not long after having delivered the FA Cup to the club.