Boro signed the 34 year old over the summer after he was released by Manchester United having fallen out of favour with former United boss Louis van Gaal.
"He's the player who we wanted to bring in because he's an amazing keeper and a leader in the changing room.
"At the beginning he wasn't at the level he is now but it is understandable. He came from a long period of not playing and before that he came from Barcelona.
"For him it was difficult at the beginning. Maybe I helped him, I had a few meetings with him and now he's doing well.
"As a player I had similar experiences. I have the same mentality as a coach that I had when I was a player. I lived in my career something similar to Victor here."