Van Persie has endured a busy period after United's failed league campaign in 2013-14, helping the Netherlands reach the FIFA World Cup semi-finals in Brazil.
The Dutch striker, 30, will be put on ice by Van Gaal, who ruled out Van Persie for their home league opener against their south Wales opponents on August 16.
"Robin wants to play every game, I know that, but so do the other 30 players in the squad. But players have to train and Robin needs a full training regime behind him before he can play again," Van Gaal said, following United's 3-1 win over Real Madrid in Michigan.
"Robin will begin training on Monday, but he won't play in the friendly against Valencia on August 12, definitely not. And he won't play in the Premier League at the start either, I think.
"People can criticise me for that decision but I know what you have to do with players who have had three weeks' holiday. Hopefully, Robin will get his fitness back very fast. But at this moment, he won't be playing."
United will take on Liverpool in the International Champions Cup final in Miami on Monday, after dispatching of the European champions courtesy of an Ashley Young brace in front of 109,318 fans.
"Three hundred thousand fans have watched us already and now we're in the Miami final, it [the total] will be even more than that," the Dutch tactician said.
"Broadcasters all over the world should show the first goal [by Young] – it was a fantastic goal by Manchester United.
"I think all the team touched the ball [in the build-up]. People could have come to the stadium just for that goal, I think."
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