Darmian left United this season for Parma.
"Paul is my friend and I have an excellent relationship with him," Darmian told the Guardian.
“First of all: we are talking about a real champion here, a great footballer, but even they can have some periods when they don't do as well [as they would like].
“The real 'problem' with Pogba at United, I think, was the price the club paid for him and that conditioned the way people perceived him.
“There has been a lot of unjustified criticism towards Pogba, for example that he doesn't work hard enough, but he always gave his best, I can assure you, in every training session.
“In my opinion his performances were good in recent years, they talk about him too negatively [in the UK].
“Did I see Pogba unhappy or willing to leave? No, I honestly didn't see him sad or unhappy, quite the opposite, for all the time I was in Manchester, Paul was absolutely happy with his decision to go back there.
“He really cares about doing well at Manchester United."