The 19-year-old, in Pretoria with his country for the Confederations Cup, said former Milan coach Ancelotti was a key figure in his development following a £17million move from Brazilian club Internacional last summer.
"'Carlo Ancelotti is a coach and a person who is very important to me," Pato told Italian newspaper Corriere della Sera. "He wanted to bring me to Milan and it was he who made me grow as a player.
"I feel I owe him a lot. It was him who wanted Milan to sign me, and he who has developed me as a player.
"But I have a contract with Milan and it is up to Milan to decide my future."