Chelsea manager Mourinho won the Treble with Inter.
"I've never been at a club where the players talked so much about a previous manager as they did about Jose Mourinho at Inter," Forlan wrote in The National.
"I arrived only a year after he had left, but the club worked through four managers in little over a year.
"Mourinho had left Inter as the treble winners: champions of Europe and Italy's league and cup, but none of his successors came close to matching his achievements.
"It wasn't just the players who loved him, everyone at the club did. I was told that the door was always open for his return.
"For so many players to speak so well about a manager is a surprise but players want to work for Mourinho.
"Not only does he win trophies players feel he supports them, protects them from pressure and shields them from criticism by taking it on himself."