The guys still 26 and i believe he still has lot left in him. Even with his slump he still averages over 30 in ODI. Quite rare for a Bangladeshi batsmen. Theres something wrong with him which he needs to figure out, mindset, technique, confidence and so on.
This is where McIness should be utilized. The academy should not only be for emerging players, but also work with guys like Nafees who are struggling on the fringes.