Januzaj came through the youth ranks of Manchester United and broke into the first team in the 2013/2014 season.
A bright start to life under David Moyes fizzled out with uninspiring loan spells at Borussia Dortmund and Sunderland before Januzaj joined Sociedad permanently in the summer of 2017.
The 26-year-old looks to have found some form at the Anoeta Stadium and is looking forward to meeting his old employers in Turin, where the game is taking place because of travel restrictions in Spain arising from the coronavirus pandemic.
"I don't have to prove to anyone how good I am, I just have to believe in myself, get my games and be happy,” the Belgium international told ESPN.
"I'm really happy to go back there, the club I love. Once I'm on the pitch, there's going to be no friends because obviously, I'm playing for another club now and also I want to win the game.
"I want to go through with my team. I'm really happy to go back there to see the people but once I'm on the pitch there will be no friends."
Reflecting on his Manchester United career, Januzaj added: "I had Fergie and David Moyes, coaches that were believing in me, but then some others came in and they wanted a bit more experience in the team," the 26-year-old said of his time with the Red Devils.
"I was a young boy and when you're a young boy you have to shut up and do what people tell you to do.
"I didn't have the right coach to push me. For example, when Van Gaal came I was playing one game out of six so it was difficult and I was like 'what am I doing here?'
"The first season under Moyes I was getting game time to show myself. At Manchester United, the most disappointing thing was that I wasn't getting games."
