Darmian, whose appearances were heavily restricted last season, was given the opportunity to move elsewhere over the summer and looked set to complete a return to Serie A.
But such a move never materialised for the Italian, whose contract expires next summer but has a one year extension clause.
According to Catalan media outlet Mundo Deportivo, Barcelona manager Ernesto Valverde is disappointed with his options at the back and wants to add experience to the full-back area following the summer departure of Digne to Everton.
Darmian publicly stated his desire to leave Old Trafford in the summer having not made a single Premier League start between November and April last term but Mourinho, who values trustworthiness in a player, was clearly open to keeping him as a back-up option.
The Italian is a hard worker and a reliable pair of hands, if often unremarkable and painfully sluggish, and following the club’s failure to properly reinforce their back line, he may still have a role at this club.
A move somewhere else further down the line, however, nonetheless feels pretty inevitable. Barcelona would certainly be a surprise destination.