The Belgian midfielder picked up the injury this week and it means Van Gaal has a decision to make as to who he’ll play in the No.10 role.
Januzaj played there against Newcastle at home but Ander Herrera was drafted in for the Champions League tie against Club Brugge during the second half.
Speaking at his pre-match press conference, van Gaal confirmed Januzaj’s injury but didn’t give a timeline for his return.
“Adnan Januzaj was injured and because of that he was out of the team,” he said.
“He shall not play against Swansea.”
United have had very few injuries so far at the start of the season which is a huge improvement on last year where van Gaal’s side was ravaged with constant injury woes right from the first game where Jesse Lingard hurt his knee and was ruled out for the whole season.
In Januzaj’s absence, Herrera will be secretly rubbing his hands together because it represents an opportunity for him to get a run of games in that position.
As for the Belgian youngster, hopefully his injury isn’t too serious because he was starting to build some momentum and improved the more he played.