Pivetta has the stuff to be a top starter, but I think he should spend a year in AAA to work on three things, command of his 4 seamer (don't overthrow), developing a 2 seamer (his FB has no movement and is easy to time) to keep hitters off-balance, and refine his changeup to go with his slider.
He's exhibit A why velocity is overrated, it was when he stopped overthrowing his slider and let it rip that he started nailing hitters, he needs to trust it more, it's got a nasty break but you have to be willing to throw it for strikes to get hitters to chase. ML hitters can hit a straight FB over the middle of the plate even if it's 95-97. A two seamer, even if he only throws it 10-15% of the time, at 91-94 with some break would keep hitters from sitting on his 4 seamer. And to me the changeup is the deadliest pitch in a SP's arsenal, if you throw it right, 10 MPH off your fastball with sink, you become unhittable.
If he can't develop secondary pitches, he has potential as a closer with a 98-100 MPH FB (what he could probably throw in 1 inning stints) and a 83 MPH slider.
Altherr is just a good young player. They're putting together a nice core, no reason to break it up unless someone makes an offer you can't refuse (Altherr, Herrera, Williams, Hoskins, Kingery, Crawford, Alfaro/Knapp). They're a couple years away while this group grows up, but by 2020 this could be a heck of a lineup.
