The Dutch player moved back to Ajax for an £18million fee, after spending four years at Old Trafford and making 141 appearances for the club.
While with United, he won the Europa League, FA Cup, League Cup and Community Shield.
Following Blind’s move becoming official, Mourinho had some kind words to say about the player.
He told the club’s website: “I would like to say a big thank you to Daley Blind for everything he has done for the club since he joined in 2014.”
“I have to say, that in my 18 years of management, Daley is one of the most professional players, both on and off the pitch, that I have had the pleasure to work with.”
“I would like to take this opportunity to wish him all the very best as he rejoins his boyhood club, Ajax, and thank him from the bottom of my heart for his commitment and dedication over the past two seasons.”
The 28-year-old made the move as his role at United looked to be becoming even smaller for the coming season.
He decided to return to his boyhood club, Ajax, where he should get more game time.