Shaw suffered a double fracture of his right leg during the 2-1 defeat against PSV Eindhoven earlier this week.
The youngster, who had been establishing a promising partnership with Memphis Depay, is expected to be out of action for at least six months.
Van Gaal expressed his sympathy for Shaw but backed his side to cope with the player’s absence.
“It’s a great loss. I have said in advance of this season already that it shall be the season of Luke Shaw. He had started fantastically and everybody had seen that. It is a great miss, a great loss,” van Gaal said.
“You have to build up again a combination with the player in front of him. Memphis and Shaw were a very good combination and now you have to build up a new combination. You have to start again and that is difficult. It’s also difficult for the player who has to replace him.”
Shaw had made a blistering start to the season and he was on course to make this campaign a memorable one, culminating in the European Championships next summer. Unfortunately, football is a cruel game and his aspirations have been left in tatters. It will be difficult for him to build himself up again mentally but he will undoubtedly have the world-class support of everybody at United.