At today's LaLiga presser, Ancelotti confirmed Casemiro had asked to be sold to the English giants.
He said: "I have spoken with him. He wants to try a new challenge, and the club understands that. We would like to respect Casemior's wish, after all that he has done for the club.
"Negotiations are underway, but nothing is official yet. He is still our player but he wants to leave us. If that happens, then we have the resources to replace him."
Ancelotti was asked whether he had tried to convince Casemiro to stay.
"No, I only listened. He has helped us a lot. I listened to his wish and there is no going back. If everything goes well for him and there is an agreement, we will wish him the best and look at what we have."