Fantasy Baseball Starting Pitcher Arsenal Changes for Week 19: Pitch Mix, Velocity, Movement (2025)

August 7, 2025

Corbin's fantasy baseball starting pitcher breakouts, risers, and sleepers for Week 19 of 2025 displaying changes in their pitch mix, movement, and velocity.

Welcome back, RotoBallers, to another column that's part of my "Starting Pitcher Arsenal Changes" article series for Week 19 of the 2025 fantasy baseball season. We're diving deep into the arsenals of one veteran remaking himself and a young arm coming around. Today's article will discuss two starting pitchers who made actionable adjustments, such as a release point change or a new pitch, as well as location changes, and whether these adjustments will matter moving forward.

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 provides so much data to digest and 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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Patrick Corbin is Throwing More Cutters

Corbin introduced a cutter in 2024, which he threw more in 2025, especially over the past couple of months. He threw his cutter 18.2 percent in May, 21.2 percent in June, and 26.9 percent in July. That's notable because it gives Corbin a third somewhat viable pitch besides the sinker and slider to either side of the plate.

Corbin's cutter has been slightly less effective against right-handed hitters in 2025 (.377 wOBA, .370 xwOBA) compared to 2024 (.316 wOBA, .317 xwOBA). It's a smaller pitch sample, but Corbin's cutter usage tripled against left-handed hitters in 2025 (14.9 percent). The cutter performs as one of his best pitches to lefties, evidenced by a .311 wOBA (.276 xwOBA), slightly worse than his slider outcomes in 2025 (.244 wOBA, .249 xwOBA).

Corbin's slider typically highlighted his arsenal, with tons of downward movement at a slower velocity than his cutter. We have a slight adjustment to Corbin's cutter movement profile. His cutter lost over two inches of downward movement with an increase in velocity by more than one mph in 2025.

The main difference with Corbin's cutter involves his location change to right-handed hitters. Corbin threw his cutter more in the heart of the zone in 2024, but with a more concentrated approach, low and inside to right-handed hitters.

Unfortunately, Corbin's cutter toes a fine line when he locates it low and inside the right-handed hitters. The cutter might not generate tons of weak contact or whiffs, but it gives hitters a gyro-like slider to think twice about. That's especially notable when Corbin's slider can drop below the zone and the hitter's bat to generate whiffs.

Corbin's Changeup

Throughout Corbin's career, he has been seeking an additional pitch for whiffs and weak contact. Corbin's changeup elicits a 15.3 percent swinging-strike rate in 2025, nearly four percentage points above his career average (11.5%). It's notable because Corbin's main pitch for whiffs was the slider.

Corbin's changeup has been his best offering to right-handed hitters, which he throws 9.6% of the time, his fourth-most-used pitch. The changeup allows .257 wOBA (.227 xwOBA), with the slider (.291 wOBA, .293 xwOBA) and sinker (.322 wOBA, .361 xwOBA) being his other two quality offerings to right-handed hitters.

His outcomes against the changeup have been an issue for him against right-handed hitters throughout his career. For context, Corbin's changeup allowed a .532 wOBA (.461 xwOBA) in 2024, with a .415 wOBA (.368 xwOBA) in 2023. Corbin's changeup added two inches of vertical movement while losing an inch of arm-side fade in 2025.

He has been spotting his changeup well against right-handed hitters over the past two seasons, with a nearly identical heat map. However, the difference involves Corbin's changeup generating weak contact and whiffs in 2025 when thrown low and away from right-handed hitters compared to 2024.

In 2024, Corbin's changeup wasn't as deadly to right-handed hitters, as it elicited fewer whiffs and more hard contact. That indicates the 2025 changeup results might be fluky, given similar locations and movement profiles.

Summary

Corbin has his best ERA and xERA since 2019. That's probably why the market hasn't been as excited about Corbin since he had an ERA over 5.00 in four previous seasons. The cutter is a helpful addition, especially to left-handed hitters. Corbin's slider plays well with his slider, and the changeup gives him an additional pitch for whiffs to opposite-handed hitters.

Eury Pérez is Pumping More Heaters

After a rough first month in June, with a 6.19 ERA, 1.50 WHIP, five percent strikeout minus walk rate, and a 9.7 percent swinging strike rate across 16 innings. Pérez threw his four-seamer 50.8 percent, and the heater allowed a .303 wOBA (.342 xwOBA) in June.

His results regressed favorably for him, with a 1.29 ERA, 0.64 WHIP, 26 percent strikeout minus walk rate, and a 15.1 percent swinging strike rate in July (28 innings). Pérez was pumping his heaters 56.8 percent of the time in July, coinciding with quality results (.153 wOBA, .226 xwOBA).

The four-seam movement profile has shifted minimally, with a difference of approximately one to two inches vertically and horizontally in 2025 compared to 2023. We've seen his four-seam fade an additional inch toward his arm side while losing induced vertical break. That seems to align well with Pérez's lower arm angle and the increased side-to-side movement in his pitches.

It might be small-sample noise, but we've seen his four-seam results improve dramatically against right-handed hitters. We're dealing with a small monthly sample, but the four-seam locations seem similar. He continues to locate his four-seam toward the inside of the plate to right-handed hitters, including up and inside.

That approach should jam right-handed hitters to generate weak contact against the four-seamer. After a one-month sample of struggles, it's interesting to see him stick with the heavy four-seam approach. Pérez continues to trust the process with a near-elite pitch in the four-seam, with the fifth-best Stuff+ among starting pitchers with 20 innings pitched.

The visual above shows the leaders in fastball Stuff+. It also shows that Pérez possesses multiple elite pitches with the slider and curveball.

Pérez Added a Sweeper

After relying on the four-seam, slider, curveball, and changeup, Pérez added a sweeper in 2025. He predominantly throws his sweeper to right-handed hitters, performing as his best pitch since it allows .114 wOBA (.073 xwOBA). Sweepers typically perform better against same-handed hitters, and it's fun for Pérez to add a third breaking pitch.

From a movement profile standpoint, Pérez's sweeper is a breaking pitch between his slider and curveball. His slider tends to be more gyro-like, with little horizontal movement. Meanwhile, Pérez throws his sweeper slower than the slider, but it generates more glove-side movement.

When examining the pitch heatmaps, we see Pérez's sweeper and slider have been thrown in similar locations. That's especially helpful when those two breaking pitchers have been located low and away from right-handed hitters.

Pérez's slider and sweeper have been most effective when thrown low and away from same-handed hitters. However, we've seen instances when Pérez hung his slider toward the inside corner to right-handed hitters, leading to brutal outcomes.

Theoretically, Pérez might keep hitters guessing by throwing the sweeper and slider to right-handed hitters. So far, the sweeper has been a positive addition to his arsenal.

Can the Changeup Survive Against LHH?

When a pitcher like Pérez throws a four-seam and multiple breaking pitches, they tend to struggle against opposite-handed hitters. Pérez lowered his changeup usage to right-handed hitters in 2025 (8.5 percent), down from 14.9 percent in 2023.

Pérez's changeup results haven't been as elite to lefties, with a .419 wOBA (.279 xwOBA) in 2025, compared to his elite outcomes in 2023 (.044 wOBA, .091 xwOBA). The curveball (.177 wOBA, .318 xwOBA) and four-seam (.154 wOBA, .292 xwOBA) have been his other two effective offerings to left-handed hitters. However, the expected metrics suggest regression for the curveball and four-seam results.

Pérez's changeup added three inches of downward movement. That's important because Pérez pounds his changeup low and below the zone to left-handed hitters. That leads left-handed hitters to chase the changeup. Pérez has a unique changeup with higher velocity and over 15 inches of arm-side fade.

We can see it in the changeup heatmaps, but Pérez wildly throws his changeup in the zone 8.9 percent of the time to left-handed hitters. That's nearly 10 percentage points below his changeup zone rate to lefties in 2023. Hitters haven't been chasing the pitch often outside the zone, but we could speculate that hitters think the changeup might be a sinker or four-seam low in the zone.

Summary

After a strong month in July, Pérez's results (2.70 ERA) look more luck-based with a 4.02 xERA. However, Pérez has been showing similar skills, yet fewer whiffs might be the most concerning trend since he used to have elite strikeout potential. The sweeper has been a welcome addition, especially to keep same-handed hitters off balance. We might see opposing teams stack left-handed hitters against Pérez and see if he can maintain his success with the changeup, four-seam, and curveball. Pérez made a couple of pitch arsenal tweaks to latch onto an optimistic view for the rest of the season.

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