The Portuguese manager is keen on clearing out the deadwood in his Manchester United squad.
That includes the likes of Matteo Darmian, Marcos Rojo and Blind.
And the latter was flogged to Ajax for a fee potentially rising to £18.1m.
It comes after a season in the Premier League where he managed to finish 90 minutes just three times.
But the deal has left Bernabeu chief Florentino Perez absolutely livid and it is all because of Barcelona.
Sensational reports from Spain have suggested that because of Mourinho’s action, Barca have been allowed to purchase one of their top targets.
Don Balon, known for their extravagant stories, have reported that Los Blancos and the Catalan club are keen on Frenkie de Jong, a highly-rated youngster at Ajax.
But with Blind back at Ajax, Barcelona have been allowed to sign the 21-year-old.
It has left Perez furious, who hired Mourinho to coach Real Madrid in 2010.