The report has since been corroborated by BBC Sport, meaning that a deal that will see the 28-year-old return to his homeland for an initial €16m (potentially rising to €21m) is very close to fruition.
The Netherlands worldwide joined the Red Devils from the Amsterdam outfit during Louis van Gaal's time in charge and he was a regular during the Dutchman's two seasons at Old Trafford.
Manchester United have already signed three players in the transfer window so far, but the club's first departure has now been confirmed.
However, Blind struggled for form and fitness last season and barely featured during Mourinho's second season at the club.
Blind expected to take a pay cut to re-join the club he left to sign for United, with his passion for the club was evident in his comments earlier this month.
Blind could be a quality squad player for us next season and he would do a decent job as a left-back.
Blind made 141 appearances for United across all competitions, seeing time at center-back, left-back and midfield.
He said: "I think Daley is a fantastic player".
Ajax are reported to have agreed a fee of €16m (£14.1m) with United for the Dutch worldwide on Saturday, although add-ons could increase the fee to €21m (£18.5m).