Sometimes its best to target failed starters in their late 20's/early 30's, transition them to the bullpen and see what happens. Sometimes it works, sometimes it doesn't.
Scott Downs is the perfect example. The Jays got tremendous value out of him from 2007 to 2010. Combined 4.0 WAR over those 4 seasons.
Even look at the Jays with Brett Cecil. Failed starter, looked like he was close to being done in the organization, though instead transitioned him to a BP role and did a solid job from 2013-2016 as a late inning reliever.