The Argentina international moved to Old Trafford in a deal worth £59.7 million from Real Madrid on Tuesday, becoming United's fourth senior signing this summer.
And Van Gaal has confirmed Di Maria has immediately become part of his plans for Saturday's visit to Turf Moor as he seeks his first Premier League victory.
“He has impressed me,” Van Gaal told MUTV.
"The first training session was with all the boys and he was very impressive. The second was a little bit less so but he has to adapt to the culture and the players with whom he shall play.
"It is the other way around also: the Man United players have to adapt to his way of playing. I believe he is ready to play. He is fit enough. He played a match in Madrid and he is ready to play.
"He has a lot of hunger to play because he wants to support Manchester United. He said it in the press conference. He is a very modest guy. He wants to work for the team so I am very curious about his first appearance.”
Fellow Argentine arrival Marcos Rojo, however, is not ready to make his first appearance in a United shirt as he continues to wait on a valid work permit.
"It's only a matter of time," Van Gaal added. "I'm manager of the biggest club in the world, but I can't change the law!"