Mata confirmed reports Van Gaal has already been telling Wayne Rooney how to take a penalty.
"Yeah, he told Wazza how to shoot, but it's very good," he told the Daily Mail. "He is a manager who feels every session. Not just a game but a training session. To him, it's all important. He is very into it.
"Sometimes he sees a striker or midfielder not make the right pass, he stops the session and tells them. He loves to do that. He is very temperamental.
"I think the example with Wazza, he was right. If you face the goalkeeper you have to wait for him to go and then put the ball in the other side.
"It's easy to say it but not so easy to do it when you are in the 88th minute of a game. So you must practise. Everything he says is meant to help.
"You must have an open mind. If you are a professional player, that's basic. I have had many managers during the past years and I can learn from all of them. Now with Louis van Gaal we have a new way of working and we are all trying to adapt. Even the goalkeeper has an important role in the game-play."
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