Former United goalkeeper Van der Sar, who played with Giggs at Old Trafford, has backed the 40-year-old to succeed in his new role.
"I'm sure under the guidance of Louis he can become an even better coach or manager in the future," Van der Sar told BBC Sport.
"Even when I played with him he was busy with his coaching badges and the philosophy of the club is in the right hands with him.
"Ryan is going to be there as assistant manager and that should be enough, with his experience, to bring United in a better frame than this year."
Van Gaal will take charge of United when his role as Netherlands coach comes to an end after the World Cup.