United finished seventh last term and van Gaal was subsequently appointed as manager to replace David Moyes, but lost 2-1 at home to Swansea City in his first game last weekend.
The Dutchman endured a sluggish start to his tenure as Bayern Munich coach in 2009, but ended the campaign by leading the club to the Bundesliga title.
However, van Gaal has noted the lack of balance in United’s squad and has outlined the difficulty of winning the league this season.
“I think it would be a miracle but it is also possible,” said van Gaal. “It is always possible but it shall be very difficult.
“When I got to Bayern Munich the selection was not stable. What we did was a miracle.
“Now, this selection here was not in balance. There are five No.9s, six No.10s and so on. And we don’t have defenders.”
Van Gaal signed a three-year contract at Old Trafford upon his appointment and he is confident that United’s owners, the Glazer family, will give him time to rebuild the club.
He added: “I think the owners understand or I would not have accepted this job.
“I have discussed everything, long discussions where I have shown myself as I am always open. That is why we discussed three years for my contract, not one year.
“And what are the consequences when you are hiring me? I have told them.
“And my experience in my former clubs was always that the start was difficult. I know I give a lot of information and I know that I load the brain a lot and the players have to adapt to that situation. That is not so easy.
“Then you can say to me, maybe a little less information. But that is not possible because we have to change the way of playing football and the way of transferring my methods.
“That is not only in team meetings, that is also on the pitch every day and when I give an exercise it is always with a tactical purpose. So they have to think a lot.
“When I ask the players for their opinions, they are saying that it is different to what they are used to.”