RADIO
Corbin Young examines several fantasy baseball pitcher risers and sleepers displaying changes in their pitch mix, movement, and velocity heading into Week 4 (2025).
Welcome back, RotoBallers, to my weekly "Starting Pitcher Arsenal Changes" article series for Week 4 of the 2025 fantasy baseball season. Today's article will discuss a few starting pitchers who made actionable adjustments, like a release point change or a new pitch. For those new to this column, we cover a few starting pitchers and their arsenal changes via pitch mix, velocity, and movement each week.
One quick one in a negative direction would be Tanner Houck. In one of my starting pitcher threads, we noted Houck has been losing vertical and horizontal movement via the sweeper and splitter. Houck uses a low arm angle, with pitches moving more east-to-west, which doesn't bode well if he loses movement.
Since it's early, we're looking for new pitches, velocity, and movement changes. With these pitchers having a limited sample of starts, we can compare their previous outings and the previous season. 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 you have questions about. This is the third article of this series for the 2025 season. Thank you for reading!
Gavin Williams Has a New Sweeper
Williams wasn't a pitcher target because he missed over three months with an elbow injury in 2024. However, part of growing and learning involves taking in new information. Williams has a new sweeper that he throws primarily to right-handed hitters (43 percent). He introduced a cutter in 2024, having decent results (.266 wOBA, .282 xwOBA), but the sweeper is a better option in 2025.
Besides the four-seamer, Williams mixed in a curveball (17.7 percent), slider (14 percent), and cutter (13.2 percent) to right-handed hitters in 2024. However, Williams mainly throws two pitches with four-seamers (48.1 percent) and sweepers in the early 2025 sample versus righties.
Williams' sweeper has been a slightly slower slider with 10 inches of downward movement and 7-8 inches of glove-side sweep. The sweeper gives him a breaking pitch different than the curveball and slider while having an above-average movement profile, as seen in the visual above.
He has been burying the sweeper down and below the zone. That's more evident in the sweeper and slider zone rates. Williams throws the sweeper in the zone 31.6 percent of the time in 2025 versus a slider zone rate of 53.5 percent in 2024. Besides the zone rates, the sweeper elicits an 18.4 percent swinging strike rate, leading the arsenal.
Williams Raised His Arm Angle
Williams raised his vertical release point by three inches and shifted his horizontal release two inches closer to his midline. That led to Williams raising his arm angle closer to his 2023 one after being lower in 2024. He raised his arm angle to 38 degrees in 2025, versus 35 in 2024 and 40 in 2023.
Williams historically had elite extension over seven feet. However, he lost 2.5-3.5 inches of extension over the past two seasons. That's interesting because his arm angle shifted more toward his rookie season, leading us to wonder if it's compensation for his elbow injury in 2024 or a fluky change. He went from 7.4 feet of extension to just under seven (6.9), leading to his extension numbers going from elite to high-end.
Since Williams has good extension, even with the decline, it can help his four-seamer perform better than expected with the mediocre induced vertical break (IVB) of around 16 inches. His extension and four-seam locations in the upper third of the zone can help overcome the average IVB.
Throughout his brief career, he has been throwing a curveball with more velocity, from 76.3 mph (2023) to 79.5 mph (2024) and 81.7 mph (2025). Thankfully, Williams' curveball maintained above-average downward movement, though it lost 1.5 inches in 2025 (56.9 inches) versus 2024 (58.5 inches).
The curveball has been a weapon against left-handed hitters, evidenced by a .128 wOBA (.234 xwOBA) in 2025 versus .214 wOBA (.201 xwOBA) in 2024. That should pair well with the new sweeper since it will give him a reliable breaking pitch to attack both sides of the plate.
Summary
Williams' new sweeper has been an actionable change, though there still might be injury concerns. Since he lost 2-3 inches of extension, it's something to monitor, especially with the release points shifting closer to his rookie season. We like Williams' new sweeper, so we should weigh that change more heavily, especially if it remains effective. The control has been scary, with a 37 percent ball rate, though he boasts a career-best swinging strike rate (13 percent). Besides the sweeper, we should monitor the raised arm angle and the decline in extension.
On Wednesday against the Orioles, Williams used a similar approach against righties and lefties. He stuck with throwing sweepers and curveballs out of the zone more often, leading to whiffs. The sweeper lost three inches of downward movement and five inches of glove-side sweep, a significant change, especially with the slight (+0.7 mph) velocity increase. We still wonder if he should lower the four-seam usage and find a second pitch against either side of the plate.
Jesus Luzardo Lowered His Arm Angle
Luzardo had the highest arm angle of his career in 2024 (39.3 degrees) with his highest vertical release point. He lowered his arm angle closer to 2022 and 2023 by shifting his horizontal and vertical release points by about an inch or more. With Luzardo dealing with an elbow and back injury in 2024, one could speculate on his arm angle changing because of those issues.
Luzardo's velocity increased back toward 2023, with the sinker and four-seamer rising by over 1 mph versus 2024. Meanwhile, Luzardo's slider and changeup velocity jumped by 2-3 mph in 2025, closer toward his peak 2023 season, with a 3.77 xERA and 15 percent swinging strike rate.
The increased velocity could be a combination of health and shifting back toward his previous arm slot. That should lean into Luzardo's strengths, leading to more horizontal movement, mainly via the changeup and sinker. It's not dramatic, but Luzardo's changeup added over an inch of arm-side fade, with the sinker gaining 0.5 inches at a higher velocity for both.
That's a positive combination since pitches sometimes lose movement when they're at a higher velocity. On the flip side, we've seen Luzardo's slider lose downward movement when thrown at a higher velocity, though that's not surprising. It turned into somewhat of a bullet slider, which might not be a good thing if he hangs it in the zone.
Luzardo's New Sweeper
Luzardo's slider turned into a bullet gyro slider and lost vertical movement, but he added a new sweeper. The sweeper mirrors his slider in velocity and downward movement, though it possesses over eight inches of glove-side sweep. Theoretically, the sweeper should bode well against same-handed hitters.
Thankfully, Luzardo's sweeper has been effective against left-handed hitters, evidenced by a .183 wOBA (.143 xwOBA) in the early 2025 sample. That follows the trend of Luzardo's successful slider throughout his career, with a .166 wOBA (.157 xwOBA) and a 24.5 percent swinging strike rate against left-handed hitters (2021-25).
Summary
Luzardo has been a favorite of mine in the past, but I overlooked him, especially with the improved team context. His new sweeper and improved velocity have been the most actionable changes, with the near-elite skills to support the arsenal changes. That's evident in Luzardo's 24 percent strikeout minus walk rate and 13.2 percent swinging strike rate through 23.1 innings. Luzardo looks like the old version of himself.
Walker Buehler's Different Sweeper
The Red Sox tend to have their starting pitchers shift away from four-seamers and lean more on their non-fastballs. Buehler had been doing that by using 3-4 pitches to right-handed and left-handed hitters at a double-digit rate. However, it appears Buehler has a new or different sweeper.
Buehler throws a slower sweeper, down 2 mph from 2024. That led to the sweeper adding nearly three inches of downward movement and sweeping over an inch more to the glove side. His sweeper has an above-average movement profile after adding drop and sweep with a lower velocity.
Buehler's Release Point Changes
Besides Buehler's sweeper velocity, we've seen his horizontal move his horizontal release point farther away from his midline, shifting over an inch from 2024. However, his horizontal release point changed over four inches versus 2022, leading to an arm angle 4 degrees lower than in 2022 and 2023.
Theoretically, Buehler's horizontal release point shifting farther away from his midline while maintaining the vertical release should lead to more side-to-side movement. That's evident in his slider, sinker, changeup, and four-seamer, gaining 2-4 inches of horizontal movement with the horizontal release point shift.
That approach has been working well against right-handed hitters, with the sweeper allowing a .165 wOBA (.303 xwOBA) and sinker resulting in a .232 wOBA (.235 xwOBA). Buehler's sweeper should regress against righties, so be careful there.
However, the four-seam (.276 wOBA, .362 xwOBA) and cutter (.695 wOBA, .424 xwOBA) were crushed in the early 2025 sample versus right-handed hitters.
Meanwhile, Buehler might need to re-evaluate the approach against left-handed hitters, with the cutter (.370 wOBA, .460 xwOBA) and changeup (.325 wOBA, .158 xwOBA) being the two best offerings, as seen above. Though the sinker has a .000 wOBA allowed, it's due for regression (.505 xwOBA), and is one of his least-used pitches versus lefties. Buehler's cutter results will regress in 2025 (.199 wOBA, .379 xwOBA), but it was one of his better pitches versus lefties.
We've seen this before with pitchers adding a sweeper because it helps against same-handed hitters. Can the changeup and cutter be enough for Buehler versus lefties?
Summary
Buehler's skills and underlying metrics (4.53 xERA, 14 percent strikeout minus walk rate, 7 percent SwK) make us scared. That's similar to how we felt after evaluating his arsenal, though the horizontal release point changes and a newer sweeper would be the two primary actionable adjustments. Still, Buehler must adjust the approach against lefties, or it will be a bumpy ride as a deep league streamer.
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