Real Madrid president Florentino Perez accepts they cocked up Iker Casillas' departure.
Casillas, now of Porto, left Real last summer in controversial circumstances.
“Casillas' send-off didn't leave a good impression," Florentino told El Larguero.
“People were saying that Casillas had been kicked out of the club. I called him that evening after that first farewell and said, 'Iker, this doesn't look good, so he repeated it with all of the trophies he had won. But that's not talked about; they say that Casillas was kicked out. Casillas had gone through a rough time for two years.
"I have always defended him. He said that he felt isolated? No. I always supported him. The episode with Casillas has given us all something to reflect on. Whistling our players has got to stop. Those who whistle Casillas are whistling us, the club."