In 2014 and 2015 Dayton Moore and Ned Yost showed the world that a great bullpen could be a game-changing tool, especially in the playoffs. From 2000 to 2015, starters were averaging just under six innings per start every year except 2011 when the average was slightly over six, but after 2015 that started to drop off precipitously. This was not a coincidence.
Right now, 14 teams in baseball are still in the playoff hunt, 16 if you include the Orioles and White Sox. Of those 14, 11 are in the top half in baseball in bullpen ERA.