The Portuguese coach has paid tribute to the 54-year-old Spaniard, who died suddenly on Wednesday night in his hotel room
The 54-year-old had only been appointed as Villarreal's new coach on Wednesday and was due to be officially presented by the club on Friday, but suffered a fatal heart attack in his hotel room in Valencia.
Preciado ended Mourinho's nine-year unbeaten record at home in April 2011 with his Sporting Gijon team, and the Portuguese coach had only words of praise for his counterpart.
"I am no one to try to praise the life of Manuel Preciado, which was shattered into a thousand pieces today," Mourinho said via a latter published on the club's website.
"But as his colleague and a man of football, I would like to take this difficult moment to send my humble condolences to his family, the fans of Sporting Gijon, Racing Santander, Levante, Villarreal and of all the other clubs where he made his mark.
"Manolo was always a worthy rival, which I discovered well when he visited us in March, at Valdebebas.
"He had everything that I like about people and sportsmen: character, transparency and courage to fight against every blow, which were cruelly hard in his case.
"A man of football has left us, but also a very special person. I would like to express my support to all those who loved him.
"My memories of him will be sincere and permanent."