Ajax are believed to have agreed a £14m deal with United to re-sign the 28-year-old this summer.
Blind made over 140 appearances for Ajax before joining United in 2014, and Van der Sar has paid tribute to the Dutchman as a move draws closer.
Van der Sar told Omnisport: "I think Daley is a fantastic player. He's multi-functional, can be a left-back, centre-half and a defensive midfielder. For Netherlands and for Manchester United, he played many good games.
"I think it's no secret that we are still looking for a central defender and, if possible, it would be a great addition for Ajax to have a player with the quality of Daley to fit in the team."
Blind has been left out of the United squad for their pre-season tour of the United States.