The 19-year-old broke into the Red Devils first team last season with a string of impressive displays.
His performances led to him being called up by Belgium and he was included in the country's squad at this summer's World Cup.
"This is a big season for Januzaj," Neville wrote in his column for The Telegraph. "At this stage of his physical development you would not expect him to deliver 20 goals a season. But in two or three years I think he will, because he has the attributes of a world-class player."
Januzaj scored four goals for United in the Premier League last season.