Casemiro says the booing of Gareth Bale by sections of the Real Madrid support is wrong.
For the second game in a row the Wales international was jeered by some of the Bernabeu crowd on Wednesday, despite his side cruising to a 3-0 Champions League win over Apoel Nicosia.
Real fans have previous for booing their own - even Cristiano Ronaldo has suffered similar treatment - and Casemiro wants it to stop.
"He was a very strong player for us and I hope he continues to be so," he told Marca when asked about Bale. "With the quality he has, things will be going well for him one day."
He added: "We try to protect the players we have, we are always defending our own.
"It shows that we are a family. I defend my team-mates as if they were my family and I am with them until the end."
Manager Zinedine Zidane was asked about Bale's treatment after the win, saying: " I did not listen to the whistles, only the applause."
Bale has scored just once for Madrid in six appearances so far this term.