Manchester United manager Louis van Gaal has revealed that Robin van Persie will miss the start of the season following a lengthy post-World Cup break.The 30-year-old striker was a key component in Van Gaal's Netherlands team and helped take the Oranje to a third-place finish in Brazil. And following the conclusion of the tournament, Van Persie was allowed an extended break, meaning he has missed all of United's pre-season preparations - a fact that has led Van Gaal to rule him out of the Premier League opening weekend.“Robin wants to play every game, I know that, but so do the other 30 players in the squad," the 62-year-old said. "But players have to train and Robin needs a full training regime behind him before he can play again.“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 open their domestic season against Swansea City at Old Trafford on August 16.