RADIO
Welcome back, RotoBallers, to my weekly "Starting Pitcher Arsenal Changes" article series for Week 14 of the 2024 fantasy baseball season. Today's article will discuss Tanner Bibee and Bailey Ober. 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.
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. We're over two months into the season with a decent sample size of starts in 2024, and we'll compare the current and past information. This one is a bit beefier than usual, and for a good reason.
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Tanner Bibee is Throwing the Slider More to Lefties
In Bibee's rookie season, his four-seamer had mediocre pitch shape metrics, given his average Induced Vertical Break (IVB) of 16.5 with 4.6 inches of arm-side horizontal movement. With Bibee lacking an above-average fastball, it seemed logical for him to use the slider, curve, and changeup more often.
That hasn't occurred against right-handed hitters, but more so against lefties. Bibee upped the slider usage from 13.7 percent (2023) to 22.5 percent (2024) against opposite-handed hitters. The slider results improved with a .200 wOBA and 15.7 percent swinging strike versus lefties in 2024 compared to a .231 wOBA and 8.8 percent swinging strike rate in 2023.
Interestingly, Bibee throws his slider over 1 mph harder. That led to the slider dropping over six inches fewer while sweeping 1.5 inches fewer compared to 2023. The locations of the sliders remained the same, with about 40 percent of his sliders located down and inside the left-handed hitters.
So, why is Bibee's slider losing downward movement and sweeper less often? It seems related to Bibee's vertical release point dropping 1.5 inches, with his horizontal release 3.6 inches farther away from his midline.
We've seen a downward trend in Bibee's horizontal release every month throughout 2023 and 2024. That indicates Bibee's horizontal release point gradually moved toward the third baseline. Besides the slight velocity increase on the slider, the release point changes would explain the slider losing downward movement because he theoretically wouldn't have his hands on top of the ball as often.
Let's see if the slider losing downward movement continues to find success against left-handed hitters. In 2023, Bibee's slider went from an above-average movement profile in vertical and horizontal to average in vertical drop.
The Curveball Lost Downward Movement and Added Sweep
Bibee's curveball losing downward movement doesn't surprise us due to the release point changes. Like with the slider, Bibee likely hasn't been able to have his hands on top of the ball with a more three-quarters release, causing the curveball to drop fewer inches.
Bibee's curve lost nearly 10 inches of vertical movement, though it added sweep while gaining over 2 mph of velocity. There's a chance Bibee's curveball and slider blended shapes to some extent. Regardless, the release point changes contribute to the breaking ball shape adjustments.
Contrary to the slider, Bibee's curveball hasn't fared as well against left-handed hitters. Though it's his fourth-most-used pitch against lefties, he throws it more often to opposite-handed hitters (11% of the time). With the curveball losing tons of vertical movement, the results may have regressed from 2023. In 2023, the curveball allowed a .275 wOBA (.378 xwOBA) compared to a .365 wOBA (.284 xwOBA).
The main difference involves left-handed hitters making weaker contact on the curveball, evidenced by the 94.7 mph average exit velocity (2023) down to 87.1 mph (2024). Interestingly, Bibee's curveball has elicited more whiffs, with an 8.8 percent swinging strike rate (2023) to 11 percent (2024).
Since the location of the curveballs in 2024 looks different from 2023, it might explain the improved effectiveness. In 2023, Bibee threw his curveball 31.4 percent of the time right outside the zone, either low and away or inside to left-handed hitters. However, Bibee's curveball location in those zones (Zone 13 and 14) jumped to 49 percent in 2024.
Summary
Bibee has been earning the outcomes based on his skills. The skills took a step forward in strikeout minus walk rate and swinging strike rate, mainly via the whiffs increasing on the slider and curveball by about 3-5 percentage points. Though it would make sense for Bibee to lower his four-seamer usage, the slight pitch mix change against lefties seems to be working.
Keep tabs on the release point changes because they impact the pitch shape on his breaking balls. Theoretically, we want him to maintain or add vertical movement on the breaking pitches rather than lose it. I'll take the loss on not being into Bibee in 2024 after his rookie season, but the pitch shape changes feel slightly concerning.
Bailey Ober's Changeup is Adding Downward Movement
Ober's swinging strike rate peaked in 2023 at 14.6 percent. However, his swinging strike rate fell back toward his career average in 2024 at 13.4 percent. Ober's changeup has been one of his most effective pitches from a swinging strike standpoint, evidenced by a career-best 20.3 percent swinging strike rate.
Unsurprisingly, Ober's changeup added about three inches of downward movement over the past couple of seasons, aligning with the rise in whiffs. Though Ober's changeup doesn't possess tons of drop, it turned into a slightly above-average pitch, with tons of arm-side horizontal movement of 16-17 inches.
Usually, changeups fare well against opposite-handed hitters, and that's true for Ober with a .214 wOBA (2024). His changeup results have been a career best in 2024 versus left-handed hitters, with his second-best outcomes coming in 2023. Since Ober's changeup added downward movement over the past two seasons, it supports the positive results in whiffs and weak contact.
Ober's offspeed pitch performs well against righties, which we love to see. That's evident by the .268 wOBA allowed on the changeup to right-handed hitters compared to a .260 wOBA in 2023. Hopefully, Ober continues using the changeup at a high rate, especially against lefties, because it's working well.
Ober's Slider Lost Whiffs, But Dropped More Often
Historically, Ober's slider has been his second-best offering for whiffs, but the swinging strike rate fell to 13.1 percent, three percentage points below his career average. That's surprising because Ober's slider is dropping 4-5 inches more than in 2022 and 2023. Since it's an above-average pitch from a movement profile, one might hypothesize there's a location change.
In 2023, Ober threw his slider 48.6 percent of the down and outside to right-handed hitters in Zone 14. The slider was deadly when thrown in Zone 14 with a .219 wOBA in 2023, similar to 2024 (.166 wOBA). Since Ober added a cutter, there might be a pitch classification issue regarding the swinging strike rates via the slider and cutter. However, the slider's movement profile supports the pitch's ability to generate weak contact, so buy into that sticking around.
Ober's vertical release point increased by over two inches, making it a more over-the-top release. That allows Ober's hands to generate more topspin, translating into more downward movement on his breaking ball.
The Four-Seam Isn't as Flat and Cutter Hypothesis
In the past, Ober's elite extension helped his four-seamer IVB and vertical approach angle (VAA), making it a flatter fastball higher in the zone. His four-seamer isn't coming in as flat with the higher vertical release point. That's evident in Ober's four-seamer averaging -4.3 degrees of VAA in 2022 and 2023 compared to -4.6 degrees in 2024.
That makes Ober's four-seamer less effective when it loses VAA as a prototypical pitch to locate higher in the zone, as he usually does. It could be a noisy sample, but Ober's less flat four-seamer in 2024 resulted in a .434 wOBA, over 100 points above the outcomes from 2021-2023 combined (.317 wOBA).
It's speculative, but we wonder if adding the cutter makes his four-seamer less helpful since right-handed hitters crush the cutter (.403 wOBA) and four-seam (.457 wOBA). Theoretically, adding a cutter would mean Ober's fastball might be "cutting" or gaining glove-side movement. Furthermore, Ober's four-seamer and cutter might be blending slightly at times, though the pitch movement profiles might not show it. The cutter has proven itself against left-handed hitters (with a .137 wOBA) as his best pitch versus opposite-handed hitters.
If the guesses might be correct about the cutter, Ober may want to lower the usage. In June, Ober gradually lowered his cutters thrown from 28.1 percent (June 4) to 20 percent (June 9) to 16.7 percent (June 16) to 15 percent (June 22) to 14.6 percent (June 22) in his most recent outing. Unfortunately, pitching isn't as easy to say ditch one pitch, but we'll want to keep tabs on the cutter usage, especially if it continues to cause problems with the four-seamer.
Summary
When several of a pitcher's skills remain similar to previous seasons, we want to look deeper at their arsenal, movement profile, and explanations for why. Ober used a higher vertical release point, translating into more downward movement on the slider and changeup.
Theoretically, it should mean more whiffs and weak contact for his slider and offspeed pitch. Unfortunately, it led to Ober's four-seamer becoming less flat based on the VAA. However, we wonder how the newly added cutter might impact the entire arsenal, especially the four-seamer.
Buy low on Ober because we're seeing potentially intentional changes to his arsenal and release points, which comes with needing time to work through the bumps in the road.
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