Blind has been linked with a move to Barca ahead of the winter market.
And former Barca coach Van Gaal, who signed Blind for United from Ajax, supports the deal.
He told Ziggo Sport, "Daley is definitely a Barcelona player.
"In terms of level and style of play, he fits here more than in England. A libero, a defensive midfielder, attacking left back: he can fill it all up. I think that because he can play in multiple positions, he would be quite suitable"
Last week, Blind's father, Danny, confirmed a departure from United was likely.
"That is not an illogical idea, because his contract is expiring. Man United still has the opportunity to give an option, for an extra season. They might do that, because then they can receive a higher transfer fee.
"I do not know."