The Spaniard struggled to adapt to Mourinho’s style of play when the Portuguese returned for a second spell in west London and was offloaded to United in January 2014 where David Moyes was in charge.
When Mourinho arrived at Old Trafford last summer, many United fans were concerned Mata would be shown the exit door once again.
But the 28-year-old has been in terrific form this season and is increasingly finding himself as one of the first names on the Portuguese manager’s teamsheet.
Instead of wishing to sell Mata, Mourinho sees his No10 as a confident and important player for his team.
‘When I came here people thought Mata was in trouble but I knew he wouldn’t be in trouble,’ Mourinho said after Mata had opened the scoring in United’s 2-0 win over Watford this weekend.
‘One thing was the football I wanted my Chelsea to play and the other thing I want my Manchester United to play.’
Juan Mata’s season in numbers
Games played: 31
Yellow cards: 4
Red cards: 0
Minutes played: 1,988
Mourinho said that while Mata had been unable to adapt to the way he wanted his old Chelsea team to play, he has developed at United and has found adjusting much easier this time around – perhaps suggesting that he is a better player now.
‘Mata has adapted to the football I want to play. I knew since the beginning he would be an important player,’ the Portuguese manager added.
‘I think he feels that confidence in me, that confidence in the game we want to try to play.
‘So he is happy. He is happy on the pitch and you can see it the way he plays.’