Van Gaal has laid down a few rules since taking over at Manchester United.
The Dutchman has reminded his players they must fulfil their media duties and has told the United board that next year's pre-season tour must be shorter.
And now it has emerged that Van Gaal has instructed his squad to speak to one another in English, presumably to improve unity in the ranks.
"We (the squad) only speak in English," Mata said.
"He (Van Gaal) says we have to speak in English."
Mata, who is perfectly fluent in English having arrived in the UK three years ago, does not see the new rule, or any other laid down by the new manager, as harsh.
In fact, the Spaniard has a deep respect for his new club manager, and is fully behind everything he is doing at Old Trafford.
"He is very good on and off the pitch
He is a good man and a great manager," Mata said.
"He has a lot of experience, he has won trophies in previous teams too, so it's a good chance for me to learn from him and for us to improve as a team.
"He is demanding
He is very honest, straight, speaks with everyone to his face
I think this is good, a perfect way to do it, saying what you think about the players in front of them."
Mata's respect for his new manager increased six weeks ago when he witnessed at first hand Van Gaal's Holland hammer Spain 5-1 in the World Cup.
"That game was very, very bad for us," said Mata, who watched on from the bench.
"They scored five goals against Spain so he did a great job."
Van Gaal plans to implement the 3-5-2 formation he used in the latter stages of the World Cup at United this season.
That is good news for Mata, who is the perfect candidate to play in the hole behind two strikers.
Mata enjoyed two successful years at Chelsea in that position, winning the club's player of the year award on both occasions.
But under David Moyes, Mata was often stationed on the right wing, where he did not look comfortable at all.
The former Valencia midfielder hopes Van Gaal's new system will bring the best out of him.
"If I play behind the two strikers it's a good position (for me)," he said.
"I can look for the ball, I can try to assist or score, so I will try my best.
"I will try to score as much as I can and try to help the team from that position.
"If I have to play on the wing I will try my best as well but I feel comfortable in this role."
United have adapted to the new formation straight away, beating the Los Angeles Galaxy 7-0 in Van Gaal's first game in charge on Wednesday night.
And Mata hopes the system will be just as effective in the Premier League.
"It can be very dangerous for the opponent
It is difficult for them to play against us in this formation," he said.
Finishing seventh last year is an experience Mata will never forget, even though he was only at the club for the last four months of the season.
The Spaniard is aiming for the highest finish possible this term.
"Last season was my first season in England without trophies so hopefully this new season I will be back to win something," said Mata, who will play against his former club Valencia at Old Trafford on August 12.
"The Premier League is a trophy I have never won so it would be a dream for me.
"Ever since I was young Manchester United was winning trophies or fighting for them so that is what we have to do.
"We have great players, a great manager
We have to go step by step but Man United always play for winning."
Source : PA
Source: PA