Mata was a fans favourite at Stamford Bridge, and had won Chelsea’s player of the year for two seasons running.
However, he fell out of favour following the arrival of Mourinho in the summer and ended up completing a shock move to Old Trafford last month.
Now Mata has revealed his former boss was supportive of the move and ‘sympathetic’ to his feelings.
The Spaniard said: “We spoke and [Mourinho] said that he thought this was a good option for me, and I told him I thought this was a good option for me.”
“I wasn’t playing, and to be honest, I am happy when I play football. It’s the thing I like to do the most. He wished me good luck and told me to be good, as did everyone at the club.
“I’m very grateful for my time at Chelsea and for all the trophies I have won.”
Mata has made four starts out of a possible four under David Moyes since his switch, providing three assists for his teammates.