its been so long since the kid had a run of games (10-15 consecutive) that he is going to struggle to show his full potential, I wouldn't be at all surprised if there is a confidence / psychological issue holding him back after this long on the periphery.
3 options,
a) play him for a significant number of games (likely to be too big a risk for a new manager)
b) Loan him out, seems he is thought to be too good for that
c) Sell him, I suspect that is where this ends up.
I hope Slav will go option A, but think its more likely to be option C