Rashford scored Man United’s first goal of the night with a superb curling effort that left keeper Darren Randolph helpless in the West Ham net.
Marouane Fellaini eventually grabbed a second as United sealed progression to the semi-finals of the Cup with a 2-1 win.
When asked about Rashford’s goal, van Gaal said: “It was a great goal, I was behind him on the bench, I saw him view the gap and the corner and I shouted ‘shoot’ but to do it is much more difficult.
“I say always to him when you are in the 60 metre area you have to dribble and shoot. He has that quality and can score a lot of goals.
“He’s very focused on his work and that I admire, when you are so young and there is so much attention. He is scoring so many goals and important goals.
“He can cope with criticism also and he can say about himself, ‘yes manager you are right and I have to do that’. I think it is fantastic because there are not a lot of players who can see their self-image.”
United fans have seen plenty of youngsters burst onto the scene before fading away in recent years and there were fears that Rashford would suffer the same fate. However, the 18-year-old keeps dumbfounding the football world by scoring crucial goals in big moments for his side.
Rashford truly is something special and Wayne Rooney, fit again following injury, will find it tough to get back into the side.