This morning they offer their takes on Josh Hader and Tony Kemp, along with some other, non-PreStros. These are pretty detailed reports, so I'm not going to pull much from them. They are worth going to read for yourself.
I believe there is enough going on here to warrant a no. 4 starter ceiling for the recently turned 20-year-old. Hader is undoubtedly a long-term project, as noted by the 2017 ETA, but the wait could be worth it once he is a complete product. In the meantime, I would like to see him work on adding a slider to his repertoire as a fourth pitch. Perhaps more importantly, he will need to continue to build arm strength while improving his strength and conditioning.
Kemp has been the most consistent hitter on the loaded Lancaster roster, spraying line drives all around the diamond. The approach is the best part of his game for me, as he consistently gets himself into hitter's counts and doesn't mind a walk. Pair this with a good defensive profile at second base and the ability to play other positions (left and center), a utility profile is the most realistic role for me. Player comparison: Skip Schumaker.
*edit. In reading through the rest of the BP posts this morning, it appears that these reports, along with many more to come, will be free to read. No subscription needed. Now you have no excuse to be uninformed.