Fantasy Baseball Starting Pitcher Arsenal Changes: Pitch Mix, Velocity, and Movement (Week 5)

Welcome back to the weekly column where we cover a few starting pitchers and their arsenal changes via pitch mix, velocity, and movement. Last week's article examined MacKenzie Gore, Casey Mize, and Spencer Arrighetti. This week, we're examining two potential breakout pitchers, plus one pitcher playing on a team that we usually don't target for fantasy baseball.

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 five starts or so 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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Michael King is Using More Four-Seamers

King has been using the four-seamer more often in 2024, with a six percentage point increase from 2023. He traded fewer sinkers and sweepers for more four-seamers and changeups, which should lend itself to positive outcomes. King is using the changeup 10 percentage points more in 2024, with filthy outcomes versus right-handed hitters (31.4 percent swinging strike rate and .240 wOBA) and left-handed hitters (19 percent swinging strike rate and .220 wOBA).

Though King has been using more four-seamers, the results have been brutal against left-handed hitters with a .459 wOBA compared to a .294 in 2023. Thankfully, the changeup has been deadly against both sides of the plate, but it makes him a one-pitch pitcher versus left-handed hitters if he doesn't make adjustments.

Meanwhile, King has found success via the sweeper (.095 wOBA), four-seamer (.259 wOBA), and changeup (.240 wOBA) against right-handed hitters. 

The results have been a mixed bag for King to begin the season until he dominated against the Brewers with a season-high 17 whiffs. He joined one of 47 starting pitchers with 17 or more whiffs in a start in 2024. Eight came via the four-seamer after three total before his start against the Brewers. 

King made an interesting change by locating the four-seamer higher in the zone. Seven of King's eight four-seamer whiffs came in the upper third of the zone, as seen in the pitch plot above. His four-seamer has an average induced vertical break (IVB) at 15.7 inches, similar to 2023 (14.8 inches). Since King doesn't have a dominant four-seamer, it would be helpful to have him locate it higher in the zone regularly.

Summary

If King can locate the four-seamer up in the zone, he might unlock another level because the changeup is still an above-average pitch. King continued that approach against the Rockies on Tuesday, with five of his seven four-seamer whiffs coming in the upper third of the zone. 

The results looked brutal for King in Colorado, but an 18.1 percent swinging strike rate, including seven on the four-seam and eight on the changeup, indicates quality skills. King's challenge will involve limiting hard contact and home runs in the early goings of 2024, and therefore we'll experience some ups and downs.

Can We Trust a Rockies Starting Pitcher?

It's challenging to trust a Rockies starting pitcher. We could argue we haven't had a decent one since Jon Gray and German Marquez. However, Ryan Feltner has two games with 15 or more whiffs, making him one of 17 starting pitchers with 15 or more in 2024. Is he a legitimate starting pitcher we want on our fantasy squads?

Feltner increased his slider usage to 39 percent while throwing more four-seamers (33.8 percent). He bumped up the usage of the slider and four-seamer by 6-8 percentage points from 2023. He traded more four-seamers and sliders for fewer sinkers and curveballs, though he kept the changeups about the same. 

With more sliders, Feltner's swinging strike rate on the breaking ball stayed near the career average of 9 percent compared to 10.5 percent in 2024. Interestingly, the four-seamer added nearly two percentage points in swinging strike rate to 10.8 percent, with the changeup reaching a career-high 25.4 percent. For context, that's an average swinging strike rate for the four-seamer and below average on the slider. He may want to throw the slider less often in the zone to generate chases and whiffs.

It's a small sample in 2024, so his swinging strike rate numbers may regress closer to the career averages. Or it's a concerted effort to use his best pitches more often in 2024. Besides a 1 mph increase in velocity on the changeup, his slider and four-seamer remained the same. The movement profiles on the slider and four-seamer shifted slightly, but it doesn't look significant. However, pitchers in Colorado and away seem to have differences in pitch movement based on air density, according to past research.

Knowing that information, Feltner's pitch movement profiles might not be helpful to analyze. Against right-handed hitters, Feltner's slider (.324 wOBA and 10.6 percent swinging strike rate) and changeup (.320 wOBA and 25 percent swinging strike rate) have been the most effective early in 2024. 

Against lefties, the numbers tell a different story, with his slider performing poorly as his highest-used pitch (40.3 percent) with a .495 wOBA and 15.3 percent swinging strike rate. Interestingly, the four-seamer has a better xwOBA (.272) than his actual (.368), with the same for the changeup (.257 wOBA and .113 xwOBA) against lefties.

That indicates we could expect some regression on those two pitches, giving us more confidence in his opposite-handed splits. There's also a scenario where teams continue stacking left-handed hitters and Feltner keeps struggling, which might be masked in the overall numbers.

Summary

Once we move past the Rockies' pitcher bias, it's a mixed bag of whiffs and mediocre pitches. Feltner's IVB isn't great, with below-average marks at 13.2 inches on the four-seamer. From a vertical approach angle, Feltner's four-seamer ranks in the average range of -4.7 degrees, slightly steeper than in 2023 (-4.4 degrees). That explains the location issues and four-seamer approach changes causing hitters to crush the fastball, especially left-handed hitters. 

Feltner's changeup is a lethal offering, with the fifth-highest swinging strike rate on the offspeed pitch since 2023 among starting pitchers with 150 thrown. If he keeps hitters off-balance with the near-elite changeup to pair with an average four-seamer and slider, it might be decent enough to provide streaming pitcher value. Maybe take a chance in deeper formats, but don't hold too tightly unless we see a better four-seamer and slider.

Ronel Blanco Keeps Mixing Up His Pitches

After the no-hitter, Ronel Blanco showed us a few starts that he deserves a spot in the Astros rotation as one of their most stable starting pitchers early in 2024. Blanco moved ahead of Cristian Javier as the starting pitcher with the most whiffs on the Astros, putting Blanco in the neighborhood of the top-25 pitchers in total whiffs. 

Blanco keeps mixing up the pitch mix in each game. In two of Blanco's best games from a whiff standpoint, he used the slider and changeup more often, with a reduction in the four-seamer. Blanco's changeup has consistently been his best pitch for whiffs with a 17.4 percent swinging strike rate, with the slider eliciting the second most at 10.1 percent. 

While it's not the most dominant arsenal, Blanco's four-seamer has an above-average fastball from a movement standpoint. That's evident in the 17.8 inches of IVB and 9.2 inches of arm-side movement. Though Blanco's four-seamer lost an inch of IVB, it added nearly two inches of arm-side run. That means the fastball can generate weak contact, which we've seen against both sides of the plate.

Blanco's four-seamer results improved by over 200 points, evidenced by a .253 xwOBA (2024) against right-handed hitters and .281 xwOBA versus left-handed hitters (2024). That aligns with his fastball movement profile changes for Blanco in 2024, making it another quality offering to pair with his changeup. 

Summary

Blanco's arsenal looks better than expected, especially knowing he possesses two above-average pitches in the four-seamer and changeup. The slider is solid, especially against right-handed hitters with a .215 xwOBA and 19.1 percent swinging strike rate in 2024 compared to a .262 xwOBA and 26.5 percent swinging strike rate in 2023.

Have confidence in Blanco's success being relatively sustainable as a late-breakout pitcher, with his rotation spot seeming relatively safe with other rotation injuries and struggles. Regardless, Blanco's arsenal checks several boxes for an above-average starting pitcher.

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