Duffey dropped his curveball usage by about 18% in 2018. While the whiff rates on his hook were above average, it was absolutely crushed with a .533 wOBA on contact. Duffey should continue to decrease his curveball usage in favor of his superior slider.
Duffey ditched his sinker, using the four-seamer as his sole fastball in 2019 and improving his pVAL from -1.8 to 9.5. Additionally, he increased his his veloicty by a tick, which helped net a fantastic 14.9% swinging-strike rate. Duffey’s been successful at getting both called and swinging strikes with his heater.
Duffey added a slider in 2019 and it became his primary breaking pitch. While it has similar horizontal movement to his curve, it’s thrown hard and has less vertical drop. The slider provided an above-average SwStr% and induced extremly weak contact. Duffey should continue to utilize this pitch as his primary breaking ball.
While Duffey’s four-seamer gained 1.2 mph in average velocity, it lost a good amount of the movement that made it great in 2017, which showed in the results (-2.2 pVal down from 6.8 in 2018). His go-to pitch saw a four percentage-point drop in swinging-strike rate and a 17-point drop in K rate in 2018 while getting hit for a .290 BAA with a .387 ISO and a 180 wRC+. It has always been a pitch designed to create fly-ball outs (53.8 FB% in 2018, 51.4% in 2017), but this year, way too many of those fly balls ended up in the stands (21.4 HR/FB% in 2018, up from 10.5% in 2017).
On the surface, Duffey’s curveball had many of the markers of a good offering, checking off two of the Money Pitch boxes with a 40.9 O-swing% and a 15.6 SwStr% and racking up a very good 34.4 K-BB%. So why did it end up a negative pitch according to pVal (-1.3)? That was mainly due to a combination of a 38.9 LD% and a 50.0 HR/FB%, which led to a .226 ISO and a 115 wRC+ when the pitch was put into play.
Duffey’s sinker didn’t succeed in its designed purpose, as its fly-ball rate rose for the third year in a row all the way up to 36.4% with a 16.7 HR/FB%—and didn’t induce a single infield fly ball. Despite this, it still had some value (0.8 pVal) and only gave up a .206 average with a 92 wRC+. But ultimately the .256 ISO kept it from being a larger value.
Thrown just 21 times, there wasn’t much to like about Duffey’s changeup as it only had a 5.6% chase rate and did not draw single whiff. Of the three times it was put into play, two of batted balls fell infor hits. For the third year in a row, Duffey’s changeup usage has dropped drastically from 154 pitches in 2016 to 58 pitches in 2017 to the 21 times he threw it in 2018—so perhaps Duffey is phasing the pitch out of his repertoire.