With a handful of guys getting some ARB1 raises next year, like last year (Bleier, Castro, Givens), these ARB RPs could find themselves in different uniforms later this year. You have a number of upper level pitching arms that may need to move into the bullpen over the next year.
Scott, Fry and Plutko fall into this category and you could probably include Lopez in it too, given his effectiveness early in the game and his potential to be a swing-guy in a more competitive situation.
I would generally prefer to leverage these types for another year and trade them with 2 years left if the back of my pen was established, but (again) this isn't really about what I'd do.
I don't feel like RPs typically drive deals for specific players so often you just wind up accumulating some value and that's reasonable.
I always start with 'need' so here's the MLB relief pitching this year.
Teams that jump out are....