Let me improve somewhere else
Life couldn't have got off to a better start for the youngster under the watch of then manager David Moyes, with Januzaj announcing himself on the world stage with his brace on his debut Premier League start in a 2-1 win over Sunderland.
Since that moment on Wearside however his career has really failed to kick on, either at United or during his two loan spells at Borussia Dortmund and at Sunderland last season.
He returned to Old Trafford this summer but it was clear from the beginning that he wouldn't be part of Mourinho's squad, with the coach allowing him to leave for the La Liga club in a £9.8million deal.
The 22-year-old has only made three appearances thus far for Eusebio Sacristán's side, but Januzaj has thanked Mourinho for being "fair" to him and letting him "improve somewhere else".
"Jose had to make things happen very quickly and make quick decisions," Januzaj told The Daily Mail. "I had not been playing for two years."
"He is a great manager and he has been fair to me because he let me leave to improve somewhere else," the Belgian stated. "That's how the world goes and I look forward."
"I know Sir Alex is always at the end of the phone," the 22-year-old proclaimed. "The same with Giggsy and David."
"Those people will always back me," Januzaj added. "My first job now is to impress here. I'm hoping for a World Cup place. The world does not stop."
The suggestions are stupid
Januzaj's time in both Dortmund and Sunderland have been ridiculed by many, especially during his time at the Westfalenstadion. The Belgian's temporary stay in Bavaria was cut short in January failing to make a start in Bundesliga, with coach Thomas Tuchel stating that he didn't possess the correct motivation or attitude to succeed.
Similar questions were asked of Januzaj and many others during the last season with The Black Cats as they fell out of the Premier League with a little less than a whimper, but Januzaj threw out those claims stating that he always gave his best.
'If I only played for a contract, I would have stopped football right away," he admitted. "Since I was a little boy, I have loved this game. I started from age four and it's all I wanted."
"Those suggestions are stupid," the forward proclaimed. "I had very good stats when I came on."
'People were criticising me as though I was the only player playing for Sunderland," the Belgian said about his time on Wearside. "I am a young player, still learning. I always gave my best."
"I was always the one trying to make something happen," Januzaj concluded. "Sunderland have never been in the top four so you know it will be difficult."