Arrieta’s changeup supplanted the Phillies veteran’s slider as his go-to secondary pitch in 2019, posting a 28.4% K-BB rate (bolstered by an improved 15.2% swinging-strike rate) and fooling batters out of the zone at a 46.2% clip. The change also succeeded at keeping batted balls low and in play, to the tune of a 57.1% ground-ball rate and 4 degree average launch angle.
Arrieta rediscovered his curve this season after the pitch held an ugly -9.1 pVal in 2018. There is simply nothing special about it as Arrieta falls into a middling, innings-eater at best going into 2019. It’s 50% groundball rate is the highlight here!
Nothing gold can stay, the poet wrote, and that universal truth applies to the once-dominant sinker of an aging starting pitcher. In a season marred by injury, Arrieta’s sinker couldn’t capture its old magic, getting knocked around for a .306/.385/.476 triple-slash, along with a 90.4% contact rate and a double-digit walk rate.
Arrieta saw his slider’s fly ball tendencies trend upward in 2019, up 13.9% from his 2018 campaign for a 43.9% rate. Of course, the Year of the Juiced Ball (trademark pending) was the wrong time to develop a propensity for beguiling batters into elevating the ball: Arrieta’s HR/FB rate blossomed to an unsightly 32%.
Arrieta’s main offering isn’t the pitch it once was but still managed to produce an overall positive pVal (4.6). While the sinker does get a 51.3 GB%, it really lost a lot of vertical movement. From 2011-2017, the pitch’s zMOV was greater than 7.0, but in 2018, that dropped to 4.6. 2018 was also the fourth consecutive year of a decreasing K% with the pitch.
While we may never see Arrieta’s elite 2014-15 slider, 2018 saw a revamped weapon. He threw the pitch in the zone a career best 54.8% of the time and saw nice bounceback in GB% (49.2 in 2018, 31.6 in 2017) and HR/FB% (8.3 in 2018, 16.2 2017). Finally, his BB% improved for the third straight season down to 7.3.
Arrieta’s changeup’s struggles started with a lack of movement and spiraled from there. The -0.3 zMOV (vertical movement) was the lowest of his career, and with that, the pitch became very hittable. His 81.6 Contact% and 9.8 SwStr% in 2018 pale in comparison to the 50.7 Contact% and 25.2 SwStr% in 2016. Also, the change in speed compared with the two-seamer was only 5 mph, which isn’t enough to get batters out in front to get those swinging strikes.
Arrieta’s struggles with his curveball started with getting hit hard. 36.4 HR/FB% and 34.8 LD% combined with the lowest K% (29.6) since 2014 produced a -9.0 pVal in just 283 pitches thrown.
For the fourth consecutive year, Arrieta’s four-seamer usage decreased. The four-seamer is no longer a major part of Arrieta’s repertoire.