Fantasy Baseball Starting Pitcher Arsenal Changes (Week 9): Pitch Mix, Velocity, and Movement

Welcome back to the weekly column, where we cover a few starting pitchers and their arsenal changes via pitch mix, velocity, and movement. We're at a point where the pitch movement, arsenal, and velocity should tell us a story with a handful of starts under their belts. With more injuries likely coming soon, we'll want to continue identifying streaming pitcher skills or struggling pitchers with underlying metrics suggesting better results coming soon.

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 8-10 starts in 2024, so it could be legitimate or noisy by the end of the month.

Reach out to me on X if you have a pitcher you have questions about that may be included in a future article.

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Paul Skenes is Setting Records

Like his teammate Jared Jones, Skenes is one of 18 starting pitchers at 22 years or younger with 22 whiffs in a game. Jones has reached that mark twice in 2024, with Jose Fernandez and Jack Flaherty as the other two on the leaderboard. As seen below, Skenes ties for eighth with 22 whiffs in a game in the Statcast era.

The four-seamer highlighted the arsenal with 12 whiffs (29.2 percent swinging strike rate), and the eighth most on a four-seam in a game in 2024. Skenes had the splitter (15.2%) and slider (26.7%) working for swings and misses against the Cubs Friday.

Before Skenes' debut, I noticed he had tons of arm-side movement on the four-seam in the minors, but underwhelming induced vertical break (IVB). That's translating to his MLB numbers while he generated 11 of his 12 four-seam whiffs in the heart of the zone against the Cubs. Since Skenes' four-seam lacks the above-average IVB, he appears to be using the arm-side movement to his advantage with elite velocity. 

Though it's his third-most-used pitch, Skenes attempts to keep the slider lower in the zone. That should help generate regular whiffs on the breaking ball, though we hope for more separation from the fastball. Skenes' slider (19.8% SwK) and splitter (21.1% SwK) led the arsenal in swinging strike rate in the minors, so monitor these two in the majors. 

The four-seam, slider, and splitter elicited above-average swinging strike rates in Triple-A, which teased us about when he would debut in the majors. Since most pitch metrics look similar to the minor leagues, Skenes might be able to keep up the swinging strike rates.

Summary

There's a chance Skenes dominates as a rookie like his teammate Jones, though the IVB and pitch profiles vary from Jones. Skenes' four-seamer lacks the IVB we look for in a fastball, but it boasts a silly level of arm-side run, making it difficult for opposing hitters to barrel up the ball. With the unique four-seamer characteristics, Skenes possesses two secondary pitches that will continue inducing whiffs. Let's keep tabs on Skenes because the hype is through the roof. Meanwhile, Jones displays near-elite skills through the first two months. 

Javier Assad Keeps Defying the Metrics

The results for Assad make many skeptical of him maintaining these elite ratios given the expected ERA metrics. Assad's xERA of 4.11 sits over two points above his actual numbers. The skills align with the lukewarm expected numbers, evidenced by his 21 percent strikeout rate and 9 percent walk rate. Assad's control isn't as good as one might hope, with a 37.4 percent ball rate. That's more concerning when we consider the brutal 6.6 percent swinging strike rate.

Assad often pitches to contact and rarely avoids it. That's evident in his 88 percent zone contact against the sinker, while hitters made contact on the cutter and curveball 100 percent of the time versus the Braves. The lack of whiffs and pitching to contact occurred in his second matchup against the Braves, with a 95 percent zone contact rate on the sinker and 80 percent via the cutter. Assad's sinker has been a machine for called strikes, as he pounds the zone with it 64 percent of the time.  

When a pitcher allows tons of contact, we hope for weaker contact. Assad's sinker (.211 wOBA), cutter (.339 wOBA), and slider (.069 wOBA) against right-handed hitters look promising, though the expected wOBA makes us question the results. 

Meanwhile, Assad's four-seamer (.324 wOBA), sinker (.287 wOBA), and curve (.188 wOBA) highlight the arsenal against opposite-handed hitters. Assad sprinkles in a changeup 9.9 percent of the time, translating into a .111 wOBA versus lefties. The metrics hint at decent skills, with the results seemingly semi-sustainable based on the environment. It's a slim margin for error since he relies on generating weak contact based on command and location instead of whiffs.

Assad's Sneaky Good Four-Seam

Results and whiffs aside, Assad's four-seamer has sneaky good metrics. His four-seamer has the highest IVB (17 inches) of his career, with 6.7 inches of arm-side run. For context, a four-seamer with 17 inches of IVB puts it into the above-average range, with decent horizontal movement. 

Though the four-seamer boasts above-average vertical movement, it's below average in vertical approach angle of -5.1 degrees. Theoretically, Assad's four-seamer thrown in the upper third of the zone should perform better, but it doesn't. In 2024, Assad's four-seamer resulted in a .401 wOBA when thrown in the upper third of the zone. That's worse than 2023 (.313 wOBA) and 2022 (.278 wOBA).

A theory of mine relates to a pitcher's command when they throw their pitches in the shadow areas of the zone. Assad throws his four-seam in the shadow areas 8.8 percent of the time in 2024, aligning with past seasons. However, it's the best wOBA of his career for four-seamers in the shadow area, evidenced by a .254 wOBA (2024) compared to .311 wOBA (2023) and .362 wOBA (2022). The .194 xwOBA on four-seamers in the shadow section suggests the results could be better. While Assad's four-seamer isn't generating high whiff rates, it elicits weak contact since he commands his pitches well. 

Summary

Assad has the luck factors in his favor, and regression will hit home soon. In Assad's most recent start against the Braves on May 21, he had a terrible 47.1 percent ball rate, aligning with the career-worst five walks in a game. Besides the cutter, he lacks any pitches with an above-average vertical profile. However, Assad generates horizontal movement via the curveball and the slider having more than one inch of sweep than the league-average pitch movement. There might be some unquantifiable metrics to explain Assad's success, but the skills suggest being cautious moving forward. We can ride the luck factors, but he doesn't elicit the whiffs to make up for control issues or fortune going against him. 

Cooper Criswell Adds Velocity

With Garrett Whitlock suffering an injury, Criswell is earning more starts. Since Whitlock will need surgery, Criswell's spot in the rotation seems more secure. Criswell is a soft-throwing right-handed pitcher, topping out just under 92 mph for the sinker. 

In 2024 and his most recent start, Criswell added velocity on the sinker (0.9 mph) and sweeper (1.6 mph). It's a small sample of 33 innings in 2023 and 29.1 innings in 2024, but we've seen a slight uptick in velocity for Criswell.

Typically, pitchers who throw mostly sinkers (28.6 percent), changeups (28.5 percent), and sweepers (27.5 percent) don't elicit tons of whiffs. That's evident in his 8.1 percent swinging strike rate. Criswell's changeup leads the arsenal with an 11.5 percent swinging strike rate and the slider at 10.6 percent. 

His changeup possesses elite levels of vertical movement, possibly hinting at better whiff rates in the future. The changeup drops around 44 inches, translating into 22 percent more vertical movement than the average pitch. Criswell's off-speed pitch also generates a wild amount of grounders at 72.2 percent. The changeup is a dominant pitch against right-handed hitters, resulting in a .131 wOBA. Meanwhile, it's decent versus left-handers with a .283 wOBA as his most-used pitch (29.9 percent). 

The Sinker and More Extension

Criswell's sinker is generating a career-low ground-ball rate at 33.3 percent. That's over 14 percentage points below his career ground-ball rate, though it's a small sample. My first guess would be location being an issue for Criswell's sinker. It might be more luck-related since Criswell's sinker has a career-worst .365 wOBA when thrown in the shadow area, with a .162 xwOBA. 

Meanwhile, it's the opposite effect for Criswell's sinker when thrown in the heart of the zone, as it allows a .278 wOBA and .377 xwOBA in 2024. The sinker possesses tons of vertical movement and arm-side run. That typically means weaker contact, but the expected results (.450 wOBA) look better than the actual (.354 xwOBA), mainly against left-handed hitters. 

Criswell's extension increased over the past two seasons on multiple pitches, aligning with the lower vertical release point. In 2024, Criswell's vertical release sits close to five feet compared to 5.14 feet (2023) and 5.27 in 2022. His horizontal release point moved slightly farther from the midline, causing the sinker to have near-elite arm-side run and sink. Theoretically, the sinker results should regress and generate weaker contact.

Summary

The Red Sox seem to have a mold for several starting pitchers, with strengths via control. However, the low walk rate might be a mirage for Criswell, evidenced by his middling 35.6 percent ball rate in his career compared to a 37 percent ball rate in 2024. Besides the changeup movement profile, the stuff doesn't look like it should elicit whiffs, so we can't expect a jump.

In some regards, the Red Sox starting pitchers look like an organization to trust, given the sixth-best K-BB rate, 10th-best called strike plus whiff rate (CSW%), and fourth-best SIERA among qualified starting pitchers. The velocity jump probably doesn't matter much for Criswell as a soft thrower. However, there's some intrigue via the changeup and sinker, warranting intrigue as a deep-league streamer. 

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