Koeman: Van Gaal 'wasting energy' over long ball
Koeman's Southampton host West Ham at St Mary's Stadium on Wednesday after the London club were criticised by Van Gaal in his pre-match press conference prior to United's clash with Burnley.
Van Gaal refuted suggestions that United deploy long-ball tactics - which West Ham boss Allardyce accused them of following Sunday's 1-1 draw between the two sides - by presenting a graphic to journalists to show that the figures from Upton Park were skewed against his side by passes to the flanks.
The graphic indicated that West Ham had played more than 70 per cent of long balls forward, compared to less than 50 per cent by United.
However, Van Gaal's Dutch compatriot Koeman has been quick to defend West Ham's approach.
"I watched the game last Sunday," Koeman said. "I think they [West Ham] played very well. Very physically strong. Maybe it depends on whether [Andy] Carroll can start. But they showed without that player they can play good football.
"I think West Ham have always options to play in a different style. What you have to do as a manager is to play with the best of the qualities the players have.
"The most easy way to attack is a long ball, like we do sometimes, we play a long ball to [Graziano] Pelle. That means in one pass you are close to the box of the opponent.
"I prefer always to play football but sometimes it's a good option if you have a player like Carroll or like Man United has with [Marouane] Fellaini. To do something different to try a different way to score goals.
"If someone says something about the tactics, in my opinion it's losing energy. I need my energy to the players and not to the press."