Van Gaal confirmed that he heard the boos, but was adamant that he as manager must make the decisions that he sees fit.
When asked about the booing after the match Van Gaal said he was vindicated in his decision to shift Wayne Rooney to striker after Martial was replaced.
"That is the opinion of the fans," van Gaal said.
"Afterwards they shall not be disappointed by the decision of the manager. I'm very happy because I put [Rooney] again in the striker's position and he scored."