Fantasy Baseball Starting Pitcher Arsenal Changes (Week 23): Pitch Mix, Velocity, and Movement

Welcome back, RotoBallers, to my weekly "Starting Pitcher Arsenal Changes" article series for Week 23 of the 2024 fantasy baseball season. Today's article will discuss Bobby Miller and Bowden Francis. For those new to this column, each week, 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 several 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. We have about a month left in the fantasy baseball season, causing fantasy managers to make crucial decisions for the final stretch.

Pitchers can make notable changes in smaller samples, so let's see if we can find something with these two starting pitchers finding success and understand why. 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 who may be included in a future article.

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Bobby Miller Added Velocity in a Recent Outing

Against the Rays, Bobby Miller elicited the second-most whiffs (18) in a game throughout his brief career against the Rays. Miller's curveball added 1.5 mph, and the changeup gained 1.8 mph of velocity in his best start of the 2024 season. Unsurprisingly, that led to two to four inches less downward movement for the changeup and curveball.

We know the narrative around Miller involves his fastball velocity (possibly) leading to a higher risk for injury. Miller missed over two months throughout the season with a shoulder injury, so we don't want to overanalyze his 2024 data.

However, it's worth highlighting that a velocity gain may present pros and cons. The positive would mean he's healthier than earlier in the year, with the downside involving added injury risk if he ramps up the velocity again.

We've seen a gradual decline in velocity on multiple pitches, mainly via the four-seamer (1.5 mph drop) and changeup (two mph drop). The fastball has struggled against both sides of the plate.

That's evident in the four-seam allowing a .356 wOBA (.410 xwOBA) in 2024 compared to a .181 wOBA (.271 xwOBA) last season versus same-handed hitters. He increased the four-seam usage in 2024 by nearly 15 percentage points to 38.1 percent against righties.

The same trend occurred versus lefties, with a .473 wOBA (.455 xwOBA) in 2024 compared to a .363 wOBA (.341 xwOBA) last season.

It's a small sample, but home runs seem to be the issue after a five percent HR/F in 2023, ballooning to 26.3 percent against the four-seam in 2024. Since the movement profile and release points haven't shifted significantly, it might be an issue with the four-seam location for Miller.

Miller's four-seam possesses average to slightly above-average induced vertical break at 16.1 inches, which could explain hitters squaring up the heater.

In 2024, Miller has been throwing the four-seam more in the upper third of the zone at 17.1 percent, up over four percentage points from 2023 (13 percent). When Miller throws the four-seam in the upper third of the zone, it translates to a .252 wOBA (.305 xwOBA) in 2024 compared to a .217 wOBA (.250 xwOBA) in 2023.

Miller's Changeup Lost Velocity

Again, we're dealing with small samples in 2024, but Miller's changeup lost over two mph of velocity and added two inches of downward movement. The arm-side fade hasn't shifted significantly, but we would expect more whiffs via the changeup.

Unfortunately, that's not the case, with the changeup eliciting a 17.2 percent swinging-strike rate (2023), dipping to 15.8 percent (2024), though it's not a drastic change.

Miller lowered the zone rate on the changeup by six percentage points to 32.5 percent, but the chase rate dropped by 14 points. We typically want a lower zone rate with changeups and theoretically inducing chases below the strike zone.

Notably, hitters performed better against the changeup when thrown outside the zone, with a .328 wOBA in 2024 and a .155 wOBA in 2023. It's probably a good idea to bet on the changeup results improving over a larger sample, with the added downward movement.

Summary

It's not worth looking at Miller's season-long ratios because they're terrible. The luck factors haven't been in his favor, causing the ratios to balloon. Unfortunately, the control has been awful, with a 39 percent ball rate in 2024, a five-point jump from the 35 percent ball rate in 2023.

It's likely injury-related, though there's a slight concern with the 10.5 percent swinging strike rate, down from 12 percent (2023). The most likely culprit would be the injury, and we might be buying back into Miller at a depressed cost if he closes the season relatively well.

Bowden Francis Added a Splitter and Increased the Usage

After Bowden Francis's almost no-hitter, it's hard to find anyone who isn't intrigued. Francis threw a four-seamer (51.6 percent), curveball (34 percent), and slider (14.5 percent) in 2023, but he added a splitter in 2024. He lowered the curveball usage by 12 percentage points and dropped the slider by six points in favor of throwing the splitter nearly 18 percent of the time.

The splitter hasn't been a dominant pitch for whiffs, evidenced by the 10.5 percent swinging strike rate. Francis's slider leads the arsenal in swinging strike rate at 16.7 percent, over three points higher than his career average (13.6 percent).

The visual below shows the swing-and-miss or whiff rates by pitch but still paints a picture of the rolling averages.

Francis's splitter helps him against left-handed hitters, leading to his best pitch, evidenced by a .176 wOBA (.221 xwOBA). His next best pitch versus lefties is the four-seamer (.290 wOBA). However, it's worth noting his splitter performs well against right-handed hitters (.112 wOBA) in a small sample of 59 pitches.

Unfortunately, the rest of Francis's arsenal hasn't been great against right-handed hitters. His four-seam has been decent, with a .281 wOBA, yet a .349 xwOBA. Meanwhile, the curveball (.382 wOBA, .268 xwOBA) and slider (.513 wOBA, .364 xwOBA) suggest better results should be coming soon based on the expected numbers.

Francis's Four-Seamer is a Mixed Bag

Francis's four-seamer possesses nearly 18 inches (17.9) of IVB, meaning an above-average vertical movement profile. The movement profile remained similar from 2023 and 2024.

His four-seam elicits a 10.3 percent swinging strike rate, increasing from 6.8 percent in 2023. Though the IVB looks good, the vertical approach angle (VAA) hovers in the average range, with -4.7 degrees (2023) to -4.6 degrees (2024).

When Francis throws the four-seam in the upper third of the zone, it allows a .321 wOBA in 2024 compared to a .235 wOBA in 2023. That's strange for a four-seamer with above-average IVB because his heater performs better when thrown in the middle of the plate and low in the zone.

That's evident in a .220 wOBA (.337 xwOBA) in 2024 versus a .322 wOBA (.414 xwOBA) in 2023 when he throws the four-seam in the middle of the or low in the zone. It's logical to be cautious with Francis because he probably won't continue succeeding when he's pumping the heater in the heart of the zone and maintaining positive results.

Summary

Francis's xERA (4.00) aligns with his actual (4.02), meaning he earns his results with a balance of luck and skill. The strikeout minus walk rate looks similar over the past two seasons, but Francis saw his swinging-strike rate fall from 10.9 percent to nine percent in 2024.

Francis provides a floor with his above-average ball rate at 32.2 percent in 2024, nearly identical to his career average (32.4 percent). The splitter helps against left-handed hitters, but he needs another reliable pitch to attack same-handed hitters. Though his stuff doesn't pop off the page, he possesses above-average skills that we want to buy into as a streamer in most formats.

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