The 20-year-old was in good form as he set up two of United’s goals to help the Red Devils become the first team to book their place in the fifth round of the cup competition.
Martial has been a regular fixture in the United first team since his big-money transfer to Old Trafford from Monaco in the summer.
And Van Gaal believes that the young striker has the potential to write his name into Manchester United folklore if he continues his progress at the club.
Speaking at his post match news conference on Friday, Van Gaal said: “He started not so good, I think, but I said that to him and after the first 20 minutes he came into the match and he was fabulous.
“I am very happy that he is a Manchester United player because I think he shall be a great player for Manchester United for a long time.”
United now turn their attentions to their home clash against Stoke City in the Premier League on Tuesday night.
The Red Devils have won only two of their last 10 Premier League games.
MORE: Man United latest news
MORE: Arsenal latest news
MORE: Chelsea latest news
MORE: Liverpool latest news