Call it the Frankenstein Plan for building a reliever. Teams will sort through the graveyard of pitching careers and see if there are any pieces especially usable. A failed starter with great curveball spin, perhaps. A waived reliever who might've relied too much on a flat sinker. The analysts will find these guys, and go about the work of reconstructing a modern-day reliever.
Just look at the histories of most of the best bullpen arms in baseball. Josh Hader: a 19th-round pick of the Baltimore Orioles, twice traded. Kirby Yates: undrafted out of college following Tommy John surgery, bounced around four organizations. Nick Anderson: an independent ball alum, after he was a 32nd-round pick.