While Terry Francona and Andrew Miller showed that there's a better way to manage a bullpen in October for the Cleveland Indians, baseball has been moving toward expanding roles and values for relievers for a while now. Last winter, the Houston Astros paid a remarkable price in prospects to acquire hard-throwing Ken Giles from the Philadelphia Phillies, strengthening a bullpen that was already pretty good. At the deadline, the Chicago Cubs paid through the nose to acquire Aroldis Chapman from the New York Yankees, despite the fact that they already had Hector Rondon pitching well in the ninth inning. And Cleveland gave up a significant portion of its farm system to land Miller in July.
So well before this winter, when three closers signed contracts larger than any reliever has before, teams were placing a premium on impact arms in the bullpen. The demand for dominant relievers has never been higher than it is today.
As demand increases, the basic laws of economics tell us prices will rise until the supply catches up, creating a new equilibrium. So, in the wake of Miller's superb postseason, perhaps there's a new way for teams to beat the market: by being more aggressive in moving their pitching prospects to the bullpen.
For years, there has been a significant resistance to reliever conversions among top prospects, as the dramatic difference in value between a quality starter and a 60-inning reliever incentivized teams to move a guy to the bullpen only once it became clear that being a starter wasn't going to work. Miller kicked around baseball as a failed pitching prospect until 2012, when at the age of 27 he was finally moved to the bullpen on a full-time basis.