Real Madrid boss Carlo Ancelotti was jeered by fans during their 1-1 draw with Villarreal.
Fans reacted angrily to Isco's substitution for Asier Illarramendi.
Ancelotti said: "A manager is there on the pitch and makes changes because he believes it is best for the team."
"If the fans don’t understand then I’m sorry but I made the decision to give the team more balance."