The young star was brought into the action at half-time to replace a struggling Angel di Maria and immediately added another dimension to United’s game.
It was the first time in a long while that United lined up with plenty of width and Januzaj helped stretch the Sunderland defence, particularly after Wes Brown was sent off.
He also registered his first assist of the season and van Gaal was particularly pleased to see his winger contribute to the action.
“I was very happy that he registered an assist for the first time, it’s something I like to see from every player,” he told MUTV.
Ashley Young, meanwhile, was equally impressive all game on the other wing, carrying on his solid displays and against all odds, he has become one of United’s best performers under van Gaal.
United’s No.18 said of his team-mate: “He was terrific. As a winger, you want to get the ball and run at your full-back. He did exactly that, did exactly what the manager asked him to do at half-time. It was a great performance by him but it was a team performance and everyone in the team, everyone that came on, was fantastic.”
Januzaj hasn’t started many games this season but it would a surprise if he didn’t start on the right hand side again when United play Newcastle on Wednesday, with Di Maria back in the middle of the pitch.