I think Boyle's bullpen-bound, but a guy can dream on those K rates (and the stuff he has in the 5th inning). A Boyle/ Stoudt/ Antone/ Diaz/ Santillan bullpen should be a major strength, capable of shortening games similar to the Nasty Boys of 1990. IMO, Abbott, Bonnin, and Roa all also are likely bullpen guys. (And Hubbart, fwiw.)
The best SP prospect who I think has the best chance to stick is undoudtedly Petty. Second is Williamson. After that, IMO, you have to go down to new Dayton Dragon Javi Rivera.