The former Bayern Munich centre-back explained that he wanted to avoid being compared to Ramos, who is considered a Los Blancos legend.
"Number 27, which is the one I wore at Bayern Munich, is not allowed in LaLiga and the club wanted me to wear No.4," Alaba told BILD.
"Sergio Ramos is an absolute legend. His performances on and off the pitch make him a role model. But I am Alaba and I don't want to be compared to others, I want to write my own history here."
"I am very happy to be able to work with him again," Alaba added.
"As a person he is very honest, and as a coach he has an incredible amount of experience.
"On the first day, Carlo greeted me in German, so there's something left from his time in Germany. But then we spoke in English."
"We smiled to each other when we met in the dressing room for the first time," noted Alaba.
"Toni helped me a lot, especially in the beginning. He was an important factor for me when I was adapting. His wife was also a great help to my partner."