The former Manchester United center back has tipped the midfielder to become a world-class talent and has likened his abilities to those of the Arsenal playmaker.
Januzaj has burst onto the first-team scene at Old Trafford with some impressive showings at the start of the 2013-14 campaign, including a match-winning performance away at Sunderland that saw him score both goals in a 2-1 victory.
Berg, who won two Premier League titles with the Red Devils during his three years as a player at the club, has seen enough to convince him that the 18-year-old has the potential to be a global star.
"David Moyes said he lacks one or two world-class players for the team to be top in Europe but I think he has one extra world-class player coming through the ranks," he told the club's official website. "He reminds me of Mesut Ozil in terms of temperament, awareness and understanding. I said that when I first saw him. He just needs to be handled the right way and I’m 100 percent sure that the manager will know how to do it and, if not, they can always ask Sir Alex.
"People should not take these things for granted because you don’t see players like this come through very often, so supporters and fans should appreciate seeing a kid like that playing with the big players because that is something special. But we should not expect him to do it every game. Maybe the last one he played, at Cardiff, you could see that things won’t be 100 percent every time but from what he has done so far, he has been fantastic."
Januzaj, meanwhile, has been named as one of the individuals shortlisted for the BBC's Young Sports Personality of the Year award.