However, the France international has not found the back of the net in over 11 hours of football since scoring in the 1-1 draw with CSKA Moscow in the Champions League on Oct. 21.
"I think he is very talented. But we have to say, also, that he is just 20-years-old and we have to give him time," Van Gaal told reporters ahead of Tuesday's make-or-break Champions League clash against German side VfL Wolfsburg.
"That's always difficult when you are playing for a team like Manchester United because the expectations are very high.
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"But I'm convinced he should continue (in the team) and he will score at the right moment again. You cannot expect that a 20-year-old, in his first year in the Premier League, scores every week.
"I didn't expect that when he came. He was exceeding expectations at the start of his career at Man United and I know that. I have to explain that. He doesn't need that pressure to score in every match."
United, who are a point above PSV Eindhoven in group B, head into final game against leaders Wolfsburg knowing a win against the German side would see them finish at the top.
However, if PSV win at home against bottom side CSKA Moscow, a defeat or draw for United would see them drop out into the Europa League.
(Reporting by Shravanth Vijayakumar in Bengaluru; editing by Sudipto Ganguly)
