How many reliable RPs are there in the majors?
Though Hoffman has legitimate stuff, the guys who tend to fall off have either marginal stuff that the league catches up to, get injured, or get the yips (lose command of their fastball or can't make a secondary pitch work anymore - see Brogdon and his changeup).
Bullpens are safety in numbers, and it'll come down to all those fireballing young arms they've stockpiled, and their ability to identify some veterans with upside. There will be injuries, and ups and downs, if you can't find a couple arms on your AAA team to promote, you're going to struggle. If for example, Brogdon recovers his changeup, this is instantly a deep bullpen b/c he was a quality inning eater.
As we saw with Kerkering last year, when the light goes on for a big young arm, they can fly up the system as RPs.
Just need two pitches.