I think his broken confidence is partly LvG's fault as he seemed to completely suffocate all creative play during his tenure there. For example, we all know the quality of Di Maria but he flopped immensely under LvG like many players before him.The thing is, is we all know that the potential is there, that's so plain to see. He is quick, tricky, skilful and has a cannon of a shot on him. I know we were very interested when he was at PSV, and with Mourinho clearing out at Utd, would be shocked if we weren't sniffing around.
Could be good for VJ's confidence, if you played him down the right, getting him in behind defenders and pulling back balls for him, N'Koudou, Janssen and Depay would actually look decent, and open up the possibility of a 4-3-3 (The "Dutch System")
Main problem for me is his attitude, he certainly arrived at Utd with the same hype and self-confidence of Pogba, only Pogba can back it up! Maybe time spent at Utd in the subs and reserves is a massive wake up call to him, might pull his head from his arse and get him knuckling down.
Kind of similar to when we had Gio imo, the raw talent and skill is evidently there, but the party lifestyle and attitude has to potential to derail his career entirely.