Mourinho was confirmed as new Chelsea manager yesterday.
Perez told abc.es: "The door is not closed for Mourinho.
"It is difficult to understand what the media are like here but he is leaving us with sadness, I think.
"It is not easy to live with this (media) pressure, which has sometimes been unjust, verging on personal insults.
"In the end we reached a conclusion that after three years the best for him and the club was to separate but to remain good friends. Life is very long and you never know what can happen."