The 22-year-old had an unsuccessful loan spell at Celtic last season, only making three appearances for the Glasgow side before returning to Manchester.
His new Instagram post also reveals he has not returned to training with the United squad ahead of their pre-season tour.
Blackett unexpectedly broke into the first-team under Louis van Gaal and looked highly promising in the opening stages of the season. However, a red card against Leicester significantly curtailed his progression in a red shirt.
Given that the Englishman appears to still be on holiday, the signs are that Blackett won’t be gracing the first-team under Mourinho any time soon.
While undoubtedly full of potential, Blackett’s style – which places emphasis on holding onto the ball and playing from the back – does not align with Jose’s preferred type of defender (a more robust, no-nonsense character), and so it is no surprise to see him move on.