Real Madrid president Florentino Perez admits the whistles at the Santiago Bernabeu is concerning.
Iker Casillas, particularly, has been barracked by home fans this season.
Perez remarked: "I’ll take the opportunity to say that I am worried, that I’ve heard a lot of whistling in the Bernabéu. We should never cross that line where instead of making us stronger it makes us weaker. No more. Don’t let us fall into the trap."
"We should be the first to be critical, but without crossing the line. When I say the club belongs to the members, I mean the whole world. We need to unite to protect ourselves, from people who aren’t Madrid fans or who want an influence."
"We need to protect ourselves from a certain paper that is against us. Our strength lies in unity."