Preciado had on Wednesday agreed to take the reins at relegated Villarreal and was scheduled to attend a news conference at the Madrigal on Friday.
"He was a man of football who represented the best values of his profession," Spain coach Vicente del Bosque told Marca Radio from Poland where his team are preparing to start the defence of their Euro 2012 title.
"It's almost impossible to believe so much could happen around one person in such a short space of time. He was a fighter."
Del Bosque was referring to the personal tragedies that befell Preciado over the last decade when he lost his wife to cancer, his son in a road accident and his father.
The charismatic coach, with a bushy moustache and gravelly voice, always maintained a positive outlook and was characteristically blunt about the knocks he had suffered.
"Life has hit me hard," he once said in an interview. "I could have weakened and ended up shooting myself or I could look to the heavens and carry on. I preferred the second option."
His former club Sporting Gijon broke the news of his death in a statement.
GREAT SADNESS
"Sporting convey their great sadness for the loss of someone who wrote their name in our history in golden letters and send their condolences to his family in these painful moments," the relegated club said.
Preciado coached Sporting between 2006 and January this year, when he was sacked after a poor run of results.
He was Sporting's second longest-serving coach after having also worked with Racing Santander, Levante and Real Murcia among others.
Villarreal, who were hoping Preciado would lead them back in to La Liga next season after he successfully guided Levante and Sporting into the top division, said: "Villarreal wish to show their deep sorrow for the sad loss".
Preciado famously had a war of words with Real Madrid coach Jose Mourinho two years ago after the Portuguese suggested his Sporting side fielded a weakened team in a match against Barcelona.
Later that season Sporting were shock 1-0 winners at the Bernabeu where the two coaches made up.
Mourinho ended up inviting Preciado to visit Real's training facility earlier this year.
"Manolo was always a worthy opponent," Mourinho said in a statement. "He had everything I like in people and sportsmen; character, transparency and the ability to fight against setbacks that were particularly cruel in his case.
"A great football figure leaves us and above all a very special person."
