World Cup winner Mata is to feature as Chelsea travel to Swindon in the Capital One Cup third round tonight (kick-off 7.45pm).
Mourinho has told the Spain forward, who has made two starts this term after being near ever-present in his first two seasons at Chelsea, to prove his worth at the County Ground.
And Steve Holland has backed the Portuguese to further improve Mata, who was not in the squad for Saturday’s defeat of Fulham and instead trained twice over the weekend.
Mourinho’s assistant cited the example of Ronaldo, the world’s most expensive player on his move to Real Madrid, who improved his game still further at the Bernabeu.
“He (Mourinho) is always pushing, pushing the players to the maximum every day,” Holland said.
“That’s evident not just in his teams, but in the individuals he’s worked with.
“If you look at Jose’s three-year period working with Ronaldo, he’s really evolved as an individual. He’s not just a talented dribbler and runner with the ball who can score goals. He has become a top-level match-winner who wants to run in behind, make runs, threaten the goal.
“I don’t think that just happens. That comes with pushing, even if it’s the best.
“On a day-to-day basis he (Mourinho) will be pushing for signs of improvement, working to progress the individual but ultimately for the benefit of the team.”