Starting Pitcher Arsenal Changes - Pitch Mix Analysis for Fantasy Baseball (Week 6)

Corbin Young examines several fantasy baseball pitcher risers and sleepers displaying changes in their pitch mix, movement, and velocity heading into Week 6 (2025).

Welcome back, RotoBallers, to my weekly "Starting Pitcher Arsenal Changes" article series for Week 6 of the 2025 fantasy baseball season. We have a month's worth of data, and many of us may need to make tough decisions with our lineups due to injuries. Today's article will discuss a few starting pitchers who made actionable adjustments, like a release point change or a new pitch, and whether they matter.

For those new to this column, we cover a few starting pitchers and their arsenal changes via pitch mix, velocity, and movement each week. Since it's early, we're looking for new pitches, velocity, and movement changes. When we find significant release point shifts, it can potentially impact their movement profiles in 2025.

Pitchers can make notable changes in smaller samples, so let's see if we can find something with these starting pitchers. Statcast introduced pitch percentage splits by left- or right-handed batters, which adds a nice layer to compare quickly to past seasons. Let's look through my process of examining starting pitchers and their arsenals. Reach out to me on X if you have a pitcher and have questions about it. Thank you for reading!

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Dustin May's Lower Arm Angle

When pitchers have a lower arm angle, they likely have different release points. We discussed Dustin May's lower arm angle and release point changes early in April and during spring training. May has a career-low vertical release point, over 4.5 inches (4.7) lower than in 2023. Meanwhile, his horizontal release moved nearly six inches (5.9) farther from his midline, similar to 2021 and 2022.

With the lower arm angle, May's arsenal theoretically hinted at more horizontal movement. That means his pitches tend to go more east-to-west, as seen in his pitch plot from Monday against the Marlins. He lives in the zone or on the edges, but doesn't throw too many pitches up in the zone.

May's sinker maintained the movement profile with a slight fluctuation of an inch or fewer. However, May's sweeper lost five inches of drop, moving closer to 2021 and 2022. Meanwhile, the horizontal movement didn't significantly shift. When May's sweeper is cooking, it's a GIF-able one.

May's Simplified Approach

Sometimes there's early sample noise, especially via pitch mix changes, though it looks like May simplified his approach. May has been throwing sweepers and sinkers over 91 percent of the time versus righties. It's mainly been sweepers and fastballs against both sides of the plate.

May went from throwing four pitches over 10 percent of the time in 2021 and 2022 to three (four-seam, sinker, and cutter) in 2023. He simplified the arsenal against left-handed hitters by throwing sweepers (37.1 percent), sinkers (28.6 percent), and four-seamers (28.2 percent), accounting for 94 percent of his arsenal.

For context, May's four-seam, sinker, and cutter accounted for just under 80 percent in 2023 (78.8 percent), showing the somewhat simplified approach. That might help May lean more into his strengths of being an east-to-west pitch based on his arm angle.

May used to throw more changeups to left-handed hitters, around 7-10 percent in 2022 and 2023. It was effective in the small sample, with a .088 wOBA (.337 xwOBA) in 2023 and a .000 wOBA (.086 xwOBA) in 2022. May only threw four changeups in 2025, but it doesn't look like the old one in the uber-small sample.

Why would we bring up the changeup? It might help add depth to his arsenal, as a slower pitch toward the arm side. Theoretically, it might make him slightly more unpredictable, and again lean into his strengths with the lower arm angle.

Summary

The concern with May has been health and the lack of whiffs, evidenced by his 10.2 percent swinging strike rate in 2025. It's hard to compare to past seasons since we have a limited track record of only surpassing 50 innings in a season once in his six-year MLB career. There's still some evolution to May's profile, so be patient because the stuff is nasty.

Luis L. Ortiz's Cutter Location Changed

Ortiz's cutter has been brutal but could be worse against right-handed hitters (.476 wOBA, .607 xwOBA). However, the cutter has been better yet still rough against lefties (.376 wOBA, .443 xwOBA). In Ortiz's recent outings, we saw his cutters and sliders in the heart of the zone.

We want Ortiz to locate his sliders low and cutters high in the zone. Over the past two seasons, Ortiz has been throwing his cutter often in the zone at 60-61 percent of the time. However, the cutter location is higher. Theoretically, Ortiz commanding the cutter higher in the zone should help make it an effective pitch between his four-seam and slider.

Unfortunately, hitters have been crushing his cutter in the upper third of the zone in 2025 (.381 wOBA, .508 xwOBA) versus 2024 (.164 wOBA, .233 xwOBA). It's an uber-small sample, but the cutter elicits a 15.2 percent SwK in the upper third, higher than in 2024 (11.2 percent SwK). The cutter's goal should be to generate weak contact, but maybe the pitch doesn't matter if it continues to be crushed. Regarding whiffs, Ortiz's slider has been his best pitch, eliciting a 19.8 percent swinging strike rate (SwK).

Ortiz's Slider Drops More

Ortiz's slider has generated a SwK over four percentage points higher than his career average. That aligns with Ortiz's slider dropping over two inches more in 2025 with a similar velocity and induced movement profile. We've seen his slider vertical movement fluctuate throughout his career, with 37 inches in 2025, like 2023.

Though Ortiz's slider movement profile was closer to 2023, it has generated more whiffs in 2025 (19.8 percent SwK). Maybe Ortiz traded contact quality for whiffs because the slider allows a .388 wOBA (.311 xwOBA) against right-handed hitters in 2025 versus .275 wOBA (.239 xwOBA) in 2024. The 2025 slider results versus righties in 2025 have been even worse than 2023, though the movement profiles look similar.

Though the location hasn't changed much, Ortiz threw the slider more in the zone in 2025, 47.5 percent of the time, up from 40-41 percent in 2023 and 2024. With the higher zone rates, Ortiz's slider swinging strike and chase rates increase in 2025. Specifically, Ortiz's slider chase rate jumped 6-7 percentage points to 37.1 percent in 2025. That could tell us the Guardians have been working with Ortiz to trust his stuff and best pitch by throwing it more in the zone.

Ortiz's Changeup is the Wild Card

Pitchers with lower arm angles (like Ortiz) can struggle against left-handed hitters with the east-to-west arsenal. However, Ortiz's changeup has been sneaky good, allowing a .133 wOBA (.210 xwOBA) in 2025 versus lefties, as a pitch he uses often (17.9 percent). The changeup shape is different, reaching a career high in vertical movement (32.7 inches), leading to a slightly above-average profile.

Ortiz's changeup elicits a 14.8 percent SwK in 2025, his second-best pitch for whiffs behind the slider. Like the slider, Ortiz has been throwing his changeup more often in the zone at a career-high rate (48.1 percent). He threw his changeup most often to lefties in 2023, with a zone rate of 26 percent. Ortiz appears to be commanding the changeup well in the lower third of the zone while being effective.

The induced pitch movement from 2025 versus 2023 shows us the added depth for the changeup and how it fits into his arsenal, with most of the focus on the sliders and cutters.

Summary

Regression should shift toward Ortiz's favor, with a 4.13 xERA compared to his actual ERA right under 6.00 (5.96). Ortiz's control can be an issue, with a 35 percent ball rate, but he rocks a career-best SwK (13.8 percent) in 2025. There could be a Ronel Blanco-type profile for Ortiz in 2025 where he turns into a streaming pitcher with strikeout upside, especially if the luck factors regress. We were intrigued before the season, and more so after this deep dive into his arsenal.

Tanner Bibee is Throwing More Sinkers

Bibee threw a sinker eight times (0.6 percent) versus right-handed hitters in 2024. That increased to 24.2 percent in 2025 to righties. Though it doesn't generally elicit whiffs, Bibee's sinker allows a .262 wOBA (.265 xwOBA).

Interestingly, the sinker garners a hefty 61.4 percent ground-ball rate, but the rest of his arsenal is giving up home runs at a high rate. Those numbers should regress if he maintains the highest ground-ball rate of his career in the early 2025 sample, led by his sinker.

Bibee's sinker added one inch of downward movement and nearly two inches of horizontal fade. In the visual above, we notice Bibee typically doesn't have many pitches that generate above-average levels of downward movement. That seems odd because Bibee throws from a higher arm angle (51 degrees).

Bibee's arsenal has historically been effective because of the horizontal movement via the sweeper, changeup, and cutter. His cutter is a hybrid between the sweeping slider and a gyro one, evidenced by the horizontal movement, yet it lacks drop.

Theoretically, Bibee's sinker gives him a harder pitch to throw inside to right-handed hitters, potentially leading to weak contact, as we noted earlier. The induced movement profiles show us how the sinker fits into his arsenal.

Bibee's Confusing Cutter

Currently, Bibee's cutter leads his arsenal in swinging strike rate (14.4 percent), with the slider nearby (10.4 percent). That explains the drop in his swinging strike rate overall, falling over four percentage points (8.5 percent) from 2024 (12.8 percent). The cutter is a confusing pitch. It generates the most whiffs against righties, but hitters have been smashing it (.565 wOBA, .449 xwOBA).

Bibee throws the cutter as one of his four pitches used over 27 percent of the time against right-handed hitters, so it's one he relies on often. However, Bibee lowered the cutter usage from 32.9 percent to righties in 2024. It's further confusing because the rolling graphs show us the cutter used to be one of his best pitches last season.

The results against Bibee's cutter have been better versus lefties (.265 wOBA, .372 xwOBA), and we saw him lower the usage to 15.2 percent (2025), down from 20.3 percent (2024). The arsenal overall against left-handed hitters raises the most concern because of the lower whiff rates and contact quality.

Since the cutter movement profiles haven't shifted much, we would guess it's location-based. It could be a noisy small sample in 2025, but it appears Bibee's locations have been more scattered than in 2024. That shows up somewhat in Bibee having a slightly different horizontal release point, two inches closer to his midline versus 2024, while maintaining the vertical release.

Since we don't have significant reasons to suggest that Bibee's cutter is different, it might regress in his favor over time.

Summary

We can't emphasize enough that Bibee's approach against left-handed hitters concerns us. It's a positive for Bibee to throw more sinkers with a slight differential in movement, especially to right-handed hitters. He could still improve the sinker locations.

Though the cutter confuses us, the locations and feel for it appear fixable, which potentially provides a quality offering versus lefties. Bibee teased us with a 20.6 percent SwK via the cutter on Tuesday. We had more reasons for concern than optimism before Tuesday, and the early 2025 data worried us about him bouncing back soon.

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