Bergwijn was signed by Mourinho in January from PSV Eindhoven.
He told Voetbal International: "The image people have of him is exactly what he wants.
"That makes him unique, I think. Mourinho just wants to win, he radiates that in everything. At the same time, he loves his players. Before the transfer was completed, he called me, we facetimed.
"He wanted to know everything about me and of course when I would come and when I would train for the first time. Mourinho has a lot of confidence in me, which is partly why I felt at home so quickly, I think."