You're the one constantly harping on velocity.
Arrieta has enough to be a top starter if he can replicate his second half of last season, but Nola actually had a better season with similar stuff (i.e. 92-93 velocity).
Both pitchers rely on movement and command, and both are better than Pivetta and Velasquez right now.
I said nice things about Velasquez his last two starts, but he has to show his new found command is sustainable, if the new PC has taught him to gear back and not overthrow, that could be a major change - which is why pitchers are so hard to project, changes in mechanics or adding a plus secondary pitch (Neris and Garcia with the splitter) can make a huge difference.
Eflin has similar stuff to Pivetta and Velasquez, just needs a few months in AAA to work on his mechanics (integrating his lower body now that he's been able to strengthen his legs after surgery). If he has a strong first half, I can see Klentak moving Lively or Eickhoff at the trade deadline, because it could get pretty crowded, especially if Kilome, Romero and other Reading pitchers push for promotions.
All of a sudden, this staff is starting to look deeper than expected, in the bullpen, Arano, Ramos and Rios are looking pretty solid, if they have to send two of them back to Lehigh when Leiter, Hunter and Neshak return, they'll have pretty solid depth there as well.