United followed a run of four straight defeats with a goalless draw against struggling Chelsea on Tuesday.
The team’s dismal run of results – which has included them being dumped out of the Champions League in the group stages – has led to widespread speculation Van Gaal’s job is in jeopardy.
Speaking at his weekly news conference on Thursday, the Dutchman admitted United must win on Saturday to maintain any realistic hope of overturning the nine-point deficit between themselves and Premier League leaders Arsenal.
“We have to get points otherwise the gap is too big and that is why we have to do what we have to do,” Van Gaal said.
“We have to work, prepare the game, perform and then evaluate the game again. That is of course much more difficult when you don’t win than when you win.
“We need to win because we want to be at the end [of the season] in the top of the league, and not the middle of the league.”
United’s goalless draw against Chelsea was their seventh of a troubled season and sixth at Old Trafford.
Van Gaal’s side are currently on pace to score just 44 Premier League goals, which would shatter the team’s previous low of 58 set in 2004/05, when they finished third.
United’s inability to turn possession into goals has been a recurring theme this season and Van Gaal knows his future hinges on getting the goals flowing at Old Trafford once again.
“We’ve had many games like that,” Van Gaal conceded. “The way we’ve played this season, we’re more or less always the dominant team. We are almost always pressing.
“Certainly at home we have played many, many matches like that but we don’t score and that is our problem. Our problem is not to dominate the game, our problem is to score.
“Goals are the most important thing.”
Certain sections of United fans have been heard chanting Jose Mourinho’s name in recent weeks and scarves with his name alongside the club crest and colours were being sold outside Old Trafford against Chelsea.
The club’s fans have been growing increasingly restless with the lack of goals and wins but Van Gaal insists he is delighted with the support he has had during this difficult period.
“I have had bad periods at all my clubs and I have to say the best fans are here at Manchester United because in such a difficult period they were applauding about the performance of the players and that’s fantastic,” Van Gaal said.