Fantasy Baseball Starting Pitcher Arsenal Changes (Week 17): Pitch Mix, Velocity, and Movement

Welcome back, RotoBallers, to my weekly "Starting Pitcher Arsenal Changes" article series for Week 17 of the 2024 fantasy baseball season. Today's article will discuss Brayan Bello and Carlos Rodon. 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're halfway through the fantasy baseball season at the All-Star break, causing fantasy managers to make crucial decisions for the second half of the season. Pitchers can make notable changes in smaller samples, so let's see if we can find something with these two struggling starting pitchers and understand why. Let's look through my process of examining starting pitchers and their arsenals.

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Brayan Bello Set a Career-High in Whiffs

Against the Athletics on July 9, Bello set a career-high in whiffs with 23. Unfortunately, the box score showed a mixed bag since he gave up nine hits, five earned runs, two walks, and 11 strikeouts in 5.1 innings. Bello's slider elicited a 28 percent swinging strike rate and the changeup at 45.5 percent versus the Athletics. That's over twice the season-long swinging strike rate against the slider (14.1 percent) and changeup (18.6 percent).

The Athletics ranked seventh in wRC+ against right-handed pitchers over the past two weeks (133), so Bello fared well against a weak lineup playing well. It's positive to see Bello's results and strikeout skills bounce back after two brutal months. In May, Bello had a 5.66 ERA (3.84 xERA, 10.8 percent SwK), ballooning to an 8.25 ERA (4.82 xERA, 8.6 percent SwK) in June and dropping to a 4.42 ERA (3.19 xERA, 16 percent SwK) in July.

Before breaking down Bello's arsenal, we wanted to examine the skill-related metrics since he hasn't generated more whiffs like some hoped. Last season, Bello's 4.01 xERA hinted at better results due to the high home run rate (17 percent). Maybe we shouldn't have looked past the middling skills, with a 13.1 percent strikeout minus walk rate and an 11.6 percent swinging strike rate.

Unfortunately, the luck factors shifted away from his favor, mainly via the strand rate, plus more home runs in 2024. That led to Bello's xERA looking better at 3.77. Theoretically, Bello ran into some misfortune, yet the skills haven't been that enticing.

Bello's Slider Lost Downward, But Gaining Horizontal Movement

Interestingly, Bello's slider lost downward by over six inches but gained nearly four inches of horizontal movement. That's interesting because Bello's slider swinging strike rate increased by five percentage points (14.1 percent). Typically, when a slider loses vertical movement, it translates into fewer swings and misses. Sometimes, more of a sweeping slider can elicit whiffs, too.

Bello threw the slider more often by over 12 percentage points (34.5 percent) to right-handed hitters. Besides the additional whiffs, it has allowed similar results with a .359 wOBA in 2024 and .329 wOBA in 2023. The same trend occurred against lefties, increasing pitch usage by 10 percentage points in 2024. Thankfully, Bello's slider results against left-handed hitters improved slightly, with a .359 wOBA in 2024 compared to a .399 wOBA in 2023.

He has been throwing the slider more in the zone by five points, while hitters chased over eight points more often in 2024 at 30.2 percent. Bello throws a slider 1.5 mph more and possesses an above-average movement profile. The slider gives him a pitch to theoretically attack same-handed hitters, though his changeup fares well against both sides of the plate.

Bello Throws More Changeups to Left-Handed Hitters

Bello's changeup has been his best pitch, eliciting an 18.6 percent swinging strike rate. He threw it over nine percentage points more often at 40.6 percent in 2024 against left-handed hitters, with better results in 2024 (.239) compared to 2023 (.282). It's positive to see the results improve against the changeup while Bello bumps up the usage versus left-handed hitters.

The changeup movement profile hasn't shifted much, with the zone and chase rates maintaining similar levels. Part of the success involves Bello throwing the changeup down and below the strike zone 16.3 percent of the time. That's over three percentage points more often than in 2022 and 2023. The results have been dominant, evidenced by the .136 wOBA in Zones 13 and 14, below the zone.

Summary

Bello has a strange combination of metrics, including too many home runs, an underwhelming strikeout minus walk rate, and a slightly above-average swinging strike rate. The changeup has been dirty, as it his best pitch for whiffs that he increases the usage to left-handed hitters with better results. Bello's changeup location down and below the strike zone continues to be effective, though he needs something to pair with the off-speed offering. His slider added sweep and lost downward movement while generating more swings and misses. Let's see if the results on the slider catch up to the swinging strike rate because it's been a mixed bag.

Carlos Rodon is Throwing Fewer Four-Seamers

Since the beginning of the season, Rodon threw his four-seamer 57.1 percent of the time in April, down to 52.8 percent in May, 44.7 percent in June, and 37.5 percent in July. Meanwhile, Rodon has been bumping up the changeup and curveball usage over the past few months. Rodon had a 2.54 ERA in April, which rose to 3.67 in May, 7.76 in June, and 6.07 in July.

Unfortunately, the luck factors haven't been in his favor, but we'll examine the skills and pitch mix. Was the pitch mix effective? If we focus on Rodon's four-seamers, they've been crushed in June (.473 wOBA) and July (.412 wOBA) after being decent in May (.316 wOBA).

His four-seam movement profile remained consistent, with the induced vertical break (IVB) and horizontal movement shifting about half an inch. Weirdly, Rodon's four-seam elicits more in the past two months than earlier in the season. That's evident in a 14.8 percent swinging strike rate in June and July compared to 8.8 percent from March to June.

For context, Rodon's swinging strike rate on the four-seamer hovered around 13 percent in 2021 and 2022, dipping to 11.2 percent in 2023. Rodon's four-seamer generated whiffs at a higher rate in the past few seasons compared to his career average of 9.7 percent.

Since the four-seam pitch movement profile and swinging strike rate haven't shifted much, my guess would be location-related. That's evident in Rodon throwing the four-seam in the upper third of the zone at 27.4 percent of the time in 2024, up from 38-39 percent in 2022 and 2023. Theoretically, Rodon isn't using the IVB to his advantage by not having a flat vertical approach angle and locating the heater higher in the zone.

Part of the location change might be related to a lower release point (about 1.5 inches) and a horizontal release about 1.8 inches farther away from the midline of his body. It seems Rodon's four-seamer isn't garnering the same level of ride or IVB with the lower release point, causing hitters to crush it more when he doesn't keep it in the upper third of the zone. Since it's a slight adjustment, let's see if he fixes that or if it's a noisy change with the additional whiffs over the past two months.

Rodon's Changeup Added Downward Movement

The changeup is intriguing because Rodon typically thrives off his four-seam and slider. With the added downward movement, Rodon's changeup elicits a whopping 22.5 percent swinging strike rate. Rodon's changeup added about six inches more downward movement, aligning with the high swinging strike rates.

He throws his changeup to right-handed hitters, allowing a .173 wOBA. It's hard to compare to recent seasons because he hardly threw the changeup more than 5 percent of the time. Rodon's changeup has been his best pitch against right-handed hitters in 2024. Meanwhile, Rodon's slider performed best against left-handed hitters, with a .281 wOBA.

What's interesting is Rodon lowering his vertical release point slightly, which seems counterintuitive to adding more downward movement. That might suggest a different grip, or Rodon pronates extra hard, leading to more vertical movement.

Summary

Rodon's skills suggest better results, but the xERA (4.24) looks more like a streaming pitcher with strikeout upside. However, the four-seamer shape hasn't changed much, and it's mainly a location issue. Meanwhile, his changeup looks like an actionable pitch, with the added downward movement translating into whiffs and weak contact, especially to right-handed hitters. We can't expect near-elite ratios in 2021 and 2022, but the four-seam issues seem fixable, with the slider and changeup generating tons of whiffs. This might present a buy-low opportunity for the second half of the season.

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