Starting Pitcher Arsenal Changes for Fantasy Baseball: Pitch Mix, Movement, and Velocity

April 4, 2024

Corbin examines four fantasy baseball pitcher risers and sleepers displaying changes in their pitch mix, movement, and velocity heading into Week 2 (2024).

We're dealing with small samples when we're only a week into the fantasy baseball season. However, the market reacts daily to any positive or negative performances. It's important to look beyond the results and understand the skills that led to the results. Since we usually can't control for the luck factors, we want to identify skills for pitchers.

The early data points to monitor include pitch mix changes, movement profiles, and velocity. Most of those play a role in a pitcher's stuff and skills. Thankfully, Baseball Savant provides us with easily attainable data to see it live. The process for this column will involve scouring the Baseball Savant game feeds, player breakdowns, and video to see if we notice any actionable changes that carried over from spring training or notably shifted from past seasons.

After examining the changes for these starting pitchers in the early parts of the 2024 season, we'll summarize whether we should act or be patient with the data. Again, we have a small sample of 1-2 starts in 2024, so it could be legitimate or noisy by the end of the month. Reach out on X if you have a pitcher you have questions about that may be included in a future article.

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Shane Bieber's Cutter/Slider

Some people might joke when players go to Driveline Baseline, Tread Athletics, or other athletic performance facilities. However, we have valid reasons to buy into the potential changes beyond the hype videos. Shane Bieber went to Driveline to improve his velocity and fix his curveball, which struggled in recent seasons. 

Since 2020, Bieber's four-seamer velocity went from 94.1 mph (2020) to 92.8 mph (2021) to 91.3 mph (2022 and 2023). The vertical movement on his curveball had dipped from 53.6 inches (2020) to 52.8 inches (2021) to 50.1 inches (2023). Though Bieber's curve still had above-average vertical movement, it slowly shifted closer to average than above. 

The Athletic's Eno Sarris wrote about Bieber and how Chris Langin from Driveline noticed Bieber's curveball grip had changed without him noticing in recent seasons. Though we don't have access to curveball grip data, it makes sense when considering the movement changes on the curveball losing vertical movement while adding some sweep, as seen below. The negative vertical break means the pitch is adding more glove-side sweep.

It's funny because we planned on discussing Bieber's cutter having more vertical movement (four inches more), turning it into a harder slider with more drop. Sarris seems to confirm the guess that Bieber's cutter transformed into the slider, and the curve turned into the slider. The slider elicited seven whiffs (33.3 percent swinging strike rate) on April 2 against the Mariners. Baseball Savant updated its pitch classifications on the new slider for Bieber instead of the cutter that initially showed up.

Besides the breaking balls for Bieber, he threw a changeup 2.0 mph harder in his first 2024 start. It led to the changeup losing two inches of vertical movement, with two more inches of arm side fade. Bieber's changeup had a 30.8 percent swinging strike rate in his first start against the Athletics. That's nearly three times his career swinging strike rate on the changeup at 10.6 percent. 

It's a small sample since Bieber only threw 13 changeups on an efficient 83 pitches through six innings. However, it would be a career-high changeup usage if he continues throwing it as his third offering. From 2021-2023, Bieber threw the changeup 2-5 percent of the time, with the previous high in 2020 at 8.5 percent. Throwing the harder changeup more often will help him attack lefties, leading to weaker contact and more whiffs, given the arm side fade.

Summary

Since Bieber made concerted efforts to train at Driveline and improve his craft, it should make us want to buy into him more. Even if the added fastball velocity doesn't make another jump, the adjusted grips on the breakers on the sliders, curves, and cutters included, plus the changes in movement profiles, provide us with actionable evidence that this likely isn't a fluke.

He had a second quality outing of six scoreless innings with six hits, zero walks, and nine strikeouts against the Mariners. Bieber didn't elicit as many whiffs as the previous start, but he performed well against a better lineup than the Athletics. The early verdict would be to buy into the changes he made.

Dylan Cease's Slower Changeup

In Dylan Cease's first start with the Padres, he relied on his slider (44 percent), four-seamer (39 percent), and knuckle curve (12 percent) for 95 percent of his arsenal. However, Cease threw a changeup three times, but it came in 9.5 mph slower than his previously thrown off-speed pitch. It's worth noting Cease lowered his changeup usage from 12.7 percent (2020) to 7.4 percent (2021) to 2.4 percent (2022) to 3 percent (2023). 

It might be a misclassification, but Cease threw his changeup at 65.1 mph, which is over 10 mph slower than his four-seamer. With the drastic change in velocity, his changeup added 17 inches of drop and seven inches of arm side fade. That makes sense to see the movement profile changes when it slows down 10-14 mph over the past few seasons.

Summary

Since Cease hardly uses a changeup, it's not actionable. It's interesting, though, because he thrives on velocity and a nasty slider, and it's unusual to see a massive gap in pitch speed. However, the tune will change if Cease messes with a slower changeup again that serves a purpose like generating weak contact against lefties or eliciting whiffs.

Besides the hardly used changeup, Cease's best pitch against lefties is the slider, with a .298 wOBA in 2023 and a .248 wOBA in 2022. The changeup could be a potential game-changer if it's a legitimate offering versus left-handed hitters.

A New/Old Slider For Reid Detmers

In his 2024 debut, Reid Detmers threw a new slider 3 mph slower, leading to four inches more drop and more spin. Against the Orioles on March 31, it elicited four whiffs for a 26.7 percent swinging strike rate on 15 sliders thrown. Interestingly, the four-seamer generated a career-high 12 whiffs for a 22.6 percent swinging strike rate. That's two more than his previous career best of whiffs on the four-seam at 10 in August 2022. 

Throughout his career, his four-seamer had a 9 percent swinging strike rate, with the slider at 17.2 percent. It's worth noting that Detmers has tinkered with his slider. His slider averaged 85.6 mph (2021), which increased to 88.9 mph (2023). From a spin rate, velocity, and movement standpoint, it seems his slider changed back to the 2021 form. His slider dropped more in 2021, but it performed the best in swinging strike rate in 2023 at 18.7 percent compared to 17.6 percent (2021). 

It's helpful that he located many four-seamers up in the zone, with the slider down in the zone away from left-handed hitters. That's a helpful formula for a pitcher like Detmers, who uses a fastball and two breaking pitches in the slider and curve. Since he often tinkered with the slider, we'll want to see if this is an actionable attempt for him in 2024. However, it's also worth noting that Detmers, like other pitchers, tend to vary their pitches in velocity. 

Summary

Detmers may have burned people in the past, with only two months where he had an xERA under 4.00, typically meaning the skills back up the results. In June 2023, Detmers had a 2.10 ERA (3.47 xERA) and 12.6 percent swinging strike rate (SwK) with better actual results in September with a 1.88 ERA (3.87 xERA) and a 9.8 percent SwK.

Interestingly, Detmers had two of the lowest swinging strike rates in two of his best months in 2023 with the most whiffs in his worst ones, adding to the roller coaster experience. Regardless, the slider adding vertical movement should generate more whiffs and weak contact, so we'll want to keep tabs on it going into his next start. The skills exist for Detmers and it's a matter of it coming together for him.

Brady Singer Going Full Jakob Junis

The best pitch for Brady Singer has been the slider. He knew that and threw it 54 percent of the time. That's 12 percentage points above the usage in 2023, while he lowered the sinker usage to 41.8 percent. He threw the sinker 51.1 percent of the time, meaning he swapped the sinker and slider usage by percentage in his first start of 2024. The slider performed well with a 30.2 percent swinging strike rate compared to a career average of 16.6 percent. 

Even if we bake in regression, the slider is a nasty option for Singer, and we hope he adds another pitch to have more confidence besides the sinker. Interestingly, Singer threw 14 four-seamers in his first start after throwing 27 from 2020 to 2022 with zero in 2023.

When we look at the hitter splits, the slider performed decently against righties with a .297 wOBA in 2023, but the sinker did not (.425 wOBA). Against left-handed hitters, the slider remained his best pitch with a .292 wOBA, yet the sinker struggled with a .392 wOBA. 

That indicates Singer needs another pitch to be effective against either side of the plate, especially left-handed hitters, or it will become an issue. In Singer's first start, he threw seven of the 14 four-seamers (50 percent) up in the zone, which would be a positive development for his pitch mix with fastballs up and breakers down.

Summary

A few people commented and asked if Singer was fooling us again based on my post about him singing a sweet song and sucking us back in. With pitchers like Singer having a swinging strike rate of around 10 percent, we tend to have caution, especially since he only generates whiffs via one pitch in the slider. Thankfully, he generates tons of ground balls (49 percent), with a respectable career home run per fly-ball rate at 13 percent.

If Singer locates the four-seamer up in the zone, it may be the key to unlocking another level of strikeout skills. Keep tabs on Singer's four-seamer usage because when he threw it in the past, he struggled to command it, though it's a small sample of 27 four-seamers from 2020 to 2022. It's positive to see Singer throw all 14 four-seamers to left-handed hitters in his first start because that's an approach to build upon moving forward. 

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