My rating:
1. Matic- Not a future prospect, but could go on for a few seasons. Was quality for chelsea and is proven in PL, Looks a bit unlikely atm, but who knows.
2. Dier- More of a long term prospect, knows PL and can be versatile (which is always a good thing).
3. Verratti- Havn´t seen so much of him, but i would assume the hype is there for a reason (and he is a key player for PSG).
4. Khedira- Not mentioned a lot, but imo one of the best/most reliable DM´s there is. A reason why he is always a sure shot on Germany. Does also contribute a lot in attack and buildup, however, not one for the long run.
5. Weigl- Despite what mant seem to think, I don´t believe he is lightweight. Key player on BVB and rarely, if ever makes mistakes. Kinda like a young Carrick.
Thats all I could think of on the fly, but surely, there are others which I couldn´t think of at the very moment.