Mourinho dropped Mata from his squad on Saturday as Chelsea defeated Fulham 2-0 thanks to second-half goals from Oscar and John Obi Mikel at Stamford Bridge.
Mata, who scored 19 goals and provided 35 assists for Chelsea in all competitions last season, has fallen out of favour with Mourinho, with the Portuguese stating a preference for Oscar as his playmaker.
Mourinho wants Mata to improve his game when he does not have the ball, and has called on the Spain international to show improvement in Tuesday's League Cup visit to the County Ground.
"Of course he plays from the beginning against Swindon," Mourinho said.
"The people that was (sic) not playing today, they are going to play. Juan and David (Luiz) and Michael Essien, (Ryan) Bertrand, (Cesar) Azpilicueta.
"And I hope he (Mata) tells me, on the pitch, that 'you are wrong, I am the best and I have to play every game'.
"I would love that. This is to be professional and my idea is that he is a top kid and a very good professional. So I am waiting for a professional reaction.
"I have my options but the thing that I most love in football is when the players, they prove that I am wrong.
"If he proves that I am wrong, I will be 'The Happy One', because I want him to be fantastic."
Mourinho refuted suggestions that Mata should be picked purely on last season's form and added that he took the news of his axing well.
"The past is the past," he said. "What matters is now. You have to be judged for what you do now.
"I give Juan the chance to play from the beginning against Aston Villa, from the beginning against Everton, 35 minutes against Basel.
"(When he was told he was dropped), he took it the way I want. He trained this morning and my assistant, who was training with them, was telling me that he trained very, very hard."
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