The young Belgian played up top after coming on as a second half substitute in the 3-1 win against Barcelona and looked lively during his cameo.
Van Gaal praised Januzaj and indicated that his performance has given him food for thought ahead of the new campaign.
“I have to say Adnan was a big threat for 30 mins he played as a striker and that’s good to see,” he said.
United currently have Rooney, Javier Hernandez and James Wilson as the only out-and-out strikers at the club and they will need help if the team is to be successful next term.
Van Gaal has previously stated that Memphis Depay can play up front but Januzaj could certainly do a job up there if called upon. The youngster has bags of talent but just needs a platform with which he can flourish.