Van Gaal is expected to be named United manager in the coming days.
Mata told the Daily Mail: "Iâ€™ve never met him. I know what kind of history he has, the titles he has won and the kind of football he is playing with Holland. But I donâ€™t think itâ€™s good to talk about a coach who is not our manager."
If the Dutchman does replace the Welshman, he will become Mataâ€™s seventh coach in three seasons. So much for English patience and trigger-happy Spanish club presidents.
"You mean itâ€™s my fault," he laughs.
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