The 21-year-old Belgium international was allowed to leave Manchester United for the Stadium of Light on a season-long loan deal during the summer with some questioning his apparent lack of progress since he burst on to the Premier League scene as a precocious teenager.
Januzaj told the Sunderland Echo: "It is not to re-establish myself, it is just to prove to some of the people that they were wrong
I will work hard to show they were wrong over the past few years.
"Part of my mentality is to never give up
Even if something goes a bit wrong, you always have to keep working - that is what I have been doing
Now I have the chance to prove myself again."
Januzaj, who spent the first half of last season on loan at Borussia Dortmund, was handed his senior debut for United by then manager David Moyes at the start of the 2013-14 season, and the midfielder admitted he jumped at the chance of a reunion on Wearside.
He said: "I spoke with the manager and he asked me if I wanted to come here
I said that I wanted to play football
He gave me the opportunity to do that and I am really thankful for that.
""He is building a very good team here
It is still early for him to show people what he can do, he needs time to adapt to the club, of course
But I think he is doing very, very well and all of the players that have been signed are all very good players."
Source : PA
Source: PA