Brad Keller posted a 2.47 ERA, 2.06 K/BB rate, 5.76 K/9, and 52.8% grounder rate over 54 2/3 innings this season, as the 25-year-old continues to establish himself as a front-of-the-rotation option for the Royals. Keller was aided this season by an improved slider that essentially looked more like his fastball and moved like a curveball, as the right-hander told Fangraphs’ David Laurila. The first step was remaking a slider delivery that initially left Keller unable to “see the plate because my front arm was covering the catcher….I was constantly pulling off on everything, yanking my front side. I needed to clean that up and keep my shoulders more square.”
Working on advice from Royals pitching coach Cal Eldred during the league shutdown, Keller fixed his delivery and turned his slider into a prominent part of his arsenal. 38.2% of his pitches were sliders in 2020, well up from a 31.2% usage in 2019 and a 26.2% usage in 2018. As per Fangraphs’ pitch value and slider runs above average (wSL) metrics, Keller had the third-most effective slider of any pitcher in baseball, behind only Dinelson Lamet and Zach Plesac.