Van Gaal has yet to win a competitive game in charge of the Red Devils having seen his side draw 1-1 away to Sunderland a week after losing 2-1 to Swansea City on the opening day of the season.
However, the low point of LVG's reign so far came on Tuesday evening when they were humiliated 4-0 by League One side MK Dons in the Capital One Cup.
Van Gaal made 10 changes from the side that drew against Sunderland, with only goalkeeper David de Gea keeping his place, and despite having a team that contained relative unknowns such as Marnick Vermijl, Andreas Pereira, Saidy Janko and Reece James, Danny Welbeck, Anderson and Javier Hernandez were all in from the start.
Scholes believes that there can be no excuse for the dramatic capitulation at Stadium MK, and thinks Van Gaal's formation is holding the team back.
Speaking in his column in The Independent, the former England international said: "The biggest problem of all for United? Three men at the back doesn’t seem to be working for them yet. At the moment United look like they are going to concede goals too often."
"It was the same at Sunderland on Sunday. There were mistakes. They were letting Sunderland run through them. There was a worrying absence of tackles being made."
"I understand that Van Gaal is trying to make a lot of changes very quickly but the problem is the players don’t seem to have adapted comfortably to 3-5-2 yet."
"It is never easy to make a dramatic tactical change in a short space of time when you are dealing with players who have been drilled to play with a flat back four for many years. This doesn’t mean Van Gaal’s preference for 3-5-2 is wrong – change isn’t necessarily a bad thing at all and players have a responsibility to trust and believe in their manager’s methods."
United travel to Burnley this weekend and new signing Angel di Maria could be in line for his debut following his British-record move from Real Madrid.
The Argentina winger became the latest big-money arrival at Old Trafford this summer following his £59.7 million switch from Los Blancos, and he joins Luke Shaw, Ander Herrera and Marcos Rojo as the new faces at the club.
The outlay for Di Maria takes the club's spending to around £135 million, eclipsing Liverpool as the biggest spenders of the summer, with more arrivals still expected to come through the door before the September 1 deadline.
What do you think is Manchester United's main problem?