Real Madrid fans turned on Iker Casillas during the derby defeat to Atletico Madrid.
Casillas conceded another two goals at home yesterday.
Asked about the whistles from fans, Real coach Carlo Ancelotti said: "I didn't hear any whistles, I was concentrating on the game. I try to look after the playing tactics, I'm not there to listen to what the crowd does."
"When you let in a goal at the near post it's the keeper who's ultimately responsible."
Casillas commented: "The crowd have the final say and if they think they should whistle you have to accept it and respect their opinions. The way to respond is to train and play football."