The Dutch striker has managed just three Premier League goals this season and was substituted against Arsenal last weekend after having just 13 touches of the ball.
And the United boss admits that last Saturday’s clash at Emirates Stadium was a “very bad” day for Van Persie.
“I do think 13 [touches] is few for a striker,” Van Gaal said. “I want to improve that. You can count his touches on the ball but more important is how he is playing.
“It was a very bad game for him. That is why I changed him. When I change a player, it is not because he is the best player on the pitch. You are doing something wrong.
“I believe in the players. When I change them, normally, it is because they are doing something not good in their performance.
“When you pick up this match it is easy to put a question about 13 touches. OK. But strikers do not touch the ball often. That is their profession.”
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