I don't see Neris as a "fungible reliever," rather as a high ceiling/low floor gamble, he has velocity and the splitter, he needs to locate the splitter more consistently to set up his fastball and any third pitch he develops. But his splitter is a plus plus pitch.
Neris could definitely be a closer, or just end up as a "Garcia" type who looks great one game and a pinata the next.
Gomez is a "fungible reliever."