Real coach Zinedine Zidane selected his goalkeeper son for the 3-2 win over Huesca on Sunday.
Schuster said, "To me these things of parents trainers and children players I do not like.
"This usually harms the boy."
He added: "I think Zidane does not know his best team.
"I think he wants to recover Isco, Marcelo and Gareth Bale for next year."