Pato joined Corinthians last week.
"Pato has promised me that he will return in a year and a half," the Diavolo official said. "A series of injuries created a certain distance between himself and the establishment at Milanello.
"The agreement is that he goes there, stays for 18 months and then returns to Milan. That is what he told me when we embraced for the last time at Arcore."