Having provided a defence-splitting pass for Fernando Torres minutes earlier, Mata came close to a goal himself but saw his shot parried into the path of his compatriot, who this time opened the scoring.
Substitute Ramires added a second soon after as the Blues did enough against a gutsy Swindon side.
"Obviously a lot has been made of the Mata situation because he's a high-profile player," said Holland.
"The message to all of our attacking players from Jose from day one has been they need to contribute offensively in terms of their production and of course they have to contribute out of possession and defend.
"That's been the challenge not just to Juan but all of our attacking players.
"In Juan's case, if you look at his performance here, he made Fernando's chance and was involved in the goal. Those two moments - goal-making and goal-scoring actions.
"And then in injury time he's conceded the final corner of the game supporting Ryan Bertrand in the left-back spot, which is how he was all night."
Holland added: "Tonight, for sure, we're very, very pleased with Juan's contribution with and without the ball."