The first thing that comes to mind when idealizing a relief pitcher is power stuff unleashed from a simple pitch mix.
Craig Kimbrel and Kenley Jansen are frequently cited among the best relievers of their generation. For Kimbrel, it’s always been his high-octane fastball and power-breaking ball that make for a career 2.18 ERA (188 ERA+) and career 14.7 K/9 in parts of 12 seasons. And for Jansen, it’s been the cut fastball—a pitch he’s thrown 81.9 percent of the time over the course of his 12-season stretch with the Dodgers—that makes him and his career 2.