Mata left Chelsea for Manchester United in January having seemingly been frozen out by Mourinho, who returned to Stamford Bridge at the start of the 2013-14 Premier League season.
Having been named Chelsea's player of the year for two consecutive seasons, Mata played just 13 of the London club's first 22 games in the Premier League last season and Mourinho indicated on numerous occasions that the Spaniard did not work hard enough.
Mata has now joined United and although he is still struggling to nail down a starting position, the 26-year-old playmaker is convinced he is in a better place.
"For better or for worse, we had no relationship, there was no dialogue," Mata told El Pais when asked about Mourinho.
"I was not happy, but always gave the most and respected my colleagues. You never know what will happen in life."
Mata added about new United coach Louis van Gaal: "He has so much experience and I can learn a lot from him. He's tough when he has to be.
"He says things in a firm way, intensely, but then he's somebody who is very close with the players. He really likes to talk with us, to ask us what we think about the exercises that we do in training."
Since Mata arrived in England before the 2011-12 season, he has quickly gathered a large number of fans throughout the country.
But having only played 34 minutes at the World Cup for Spain, Mata reckons his homeland does not appreciate his talents.
Spain coach Vicente del Bosque has not picked the former Valencia midfielder since the World Cup.
"Maybe I feel my values more in England than in Spain," Mata said.
"Now I have not [been] mentioned but am not looking for excuses or justifications."
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