I rated Pereira since he was in the youth team, and I had time and patience for him until not so long ago, but the man is such an undefined player at 24. He's spent the last years playing in different roles and it's like he doesn't know to play in any of them at the moment.
In Spain he played mainly on both wings for Granada and Valencia if I'm not wrong. Mourinho used him in a double pivot for some games. Then he played in a midfield three for Ole, and this season mainly as a number 10. I don't free the guy from blame because if he had the quality to play in any of these roles he would have showed something solid at some point, but I think the way p career has gone hasn't helped him at all.
I think it would be good for the man to take a step back, go to a lower team and/or league and specialize on something. He's got certain tools, the occasional cross or set piece delivery and good fighting spirit, but he's yet to define himself. I don't like Lingard either and I'd sell him as soon as the transfer window opens, but at least you know his profile as a player. If someone ask me about Pereira and what kind of player he is, his best position, I don't really know what to say.
He isn't a productive attacking player, or someone with great movement off the ball. He lacks explosivity on the wings, and good positioning and ball management to play at the base of midfield. Some years ago I expected him to become a ball playing number 6 but now I think it's probably his worst position. I'm sorry for the guy and I appreciate his efforts, but I think a new challenge elsewhere would be good for everyone involved.