By: Noah Thurm If you’ve got it, you might as well throw it. Even as league-wide velocity has trended upwards (up to an average of 93.4 MPH in 2019), pitchers are increasingly turning to their offspeed pitches to get outs. The heavy reliance on breaking pitches bucks the traditional idea of “saving” your best pitch for strikeouts or dangerous situations, and league-wide data seems to support this shift in approach. To flesh this out, I compared year-to-year changes in usage rate with the corresponding year-to-year change in whiff rate for every Slider thrown since 2015. Somewhat surprisingly, there is no convincing evidence of a reduction in effectiveness when use increases. Naturally, most players are clustered around changes of 0, but across the board guys who make big jumps in Slider usage see no consistent downward trend in whiffs as we might expect. Even isolating the extremes returns much the same result: Obviously there are outliers, but it stands to reason that a high-performing pitch thrown in limited quantities will not lose its effectiveness even with a fairly large jump in usage rate. That said, what makes a good candidate for a high-use pitch, and what pitch shape is most conducive to success? To try and answer that question, I wanted to nail down which pitch characteristics contribute to the variability in year-to-year change, even though there’s no stark trend overall. Looking at the graph on the right, I wanted to know why, for example, Hunter Strickland found success and Jumbo Diaz didn’t. I conducted a Variable Importance test to try and rank average pitch characteristics by their impact on year-to-year changes in whiff rates and determine whether a particular style of Slider can best accommodate a jump in use. This lines up with our anecdote, as Hunter Strickland has averaged nearly 400 more RPM than Diaz on his Sliders across their careers. In the case of Sliders, there certainly seems to be more than one way to skin the proverbial cat, and no one spin or movement profile that performs best on its own. The most impactful pitch characteristic was Spin Rate, which makes intuitive sense. More spin generally means more movement, but for Sliders spin is necessary for both tight and looping pitches. To even attempt to identify a potentially devastating Slider, we first need to understand the mechanics of the pitch and how they’re thrown across the league. Traditionally, Sliders are thrown with a lot of gyro (think: football) spin that does NOT contribute to movement (the remaining, or “active”, spin is a combination of back- and sidespin). This produces a very low spin efficiency, which is just the percentage of total spin that is “active”. Low-efficiency/high-gyro Sliders create the appearance of “depth” and a pitch that doesn’t seem to move a whole lot (0-5 inches of horizontal break) but misses barrels with “late” break. (From @PitchingNinja, ~12% Spin Efficiency) The higher spin efficiency climbs, and the more total spin contributes to movement, the more horizontal break or “sweep” a Slider will get. The relationship between spin efficiency and horizontal movement is very strong league-wide: Back to our initial question, is there a “type” of Slider that performs better with higher use? There is no particular trend to usage rate along the efficiency/break curve, which led me to a potentially important realization: the success of high-use breaking pitches might be as influenced by the rest of a pitcher’s arsenal as much as the characteristics of the pitch itself, even when hitters don’t see them much. I’ve found that elite sliders are matched by pitches with nearly “opposite” spin and movement profiles, combining for a deadly arsenal. To illustrate this, I took a “Goldilocks” approach to our Slider curve, and picked a player at each extreme, and one right in the middle: Three players, three vastly different Sliders, all thrown well over 50% of the time. So why does each work? I’ll start with PitchingNinja starlet Chaz Roe, owner of the most gif-able Slider in the league and an average horizontal break of 22.4 inches(!!). Roe’s Slider has more sweep than a broom closet, thanks to an insane career average spin efficiency of about 89% (up to 95% before his injury this year). For context, the average MLB Slider in the statcast era has a spin efficiency of about 20.6%, so it’s no surprise Roe is generating league-dominating movement. Through 159 pitches and 93 Sliders this year Roe had yet to surrender a barrel, allowing a WOBA of just .243. Roe’s Slider has almost no vertical movement, which is easy to imagine given his release: That isn’t the only pitch of Roe’s you’ll see on your Twitter timeline, as the Sinker he throws roughly 21% of the time looks equally stupefying: The reason I think Roe (and Wisler and Garrett) are so effective is because they generate a high degree of “spread” in their arsenals by throwing pitches with divergent spin and movement. (For an in-depth discussion of the idea of arsenal “spread” and its implications for pitch design, check out my earlier article.) Looking at each of Roe’s pitches mapped by Horizontal and Vertical Break makes this really easy to understand: Roe’s insane sweeping Slider is really well matched by a 70% efficient Sinker with tons of armside run, keeping pretty much all of his offerings on a nearly-identical horizontal plane. This allows Roe to disguise the movement on his Slider because it looks enough like the Sinker right out of hand. That’s how he generates such ridiculous swings on a pitch the entire stadium knows is coming. Garrett, on the other hand, throws a much tighter Slider with a spin efficiency of roughly 16%. He generates just 0.4 inches of Horizontal Break on average, but is posting an insane .180 WOBA and 66% whiff rate so far this year. While on the surface it seems to be a less impressive pitch than Roe’s it fits into Garrett’s arsenal and plays off his other pitches equally well. Rather than the horizontal-heavy approach we saw with Roe, Garrett relies on a 95 MPH 4-Seam Fastball as his secondary pitch, controlling the vertical plane with a high-spin Fastball with almost 10 inches of “ride” above his Slider. Unlike Roe, Garrett’s pitches depart on the vertical axis out of release, making for an equally devastating combination: Amir Garrett Slider 08-23-2019 GIF Amir Garrett Fastball Along with the low efficiency, Garrett doesn’t generate much spin at all on his Slider, seemingly running counter to the results of our earlier variable importance test. To me, this reinforces the need to keep pitches in context with the broader arsenal, even when a pitcher doesn’t make much use of it. That leaves us with Wisler, our Goldilocks, who is throwing his Slider a whopping 80% of the time this year yet maintaining a 38% whiff rate. Wisler falls between Garrett and Roe by Spin Efficiency at 58% this year and around 25% average for his career. Similarly, he splits the gap in movement, with an average Horizontal Break of 11.5 inches, almost exactly splitting Roe’s 22.4 and Garrett’s 0.4 inches of movement. Wisler has the least of an “arsenal” to speak of, but plotting it on the same map gives us much the same result: Like Garrett and Roe, Wisler maintains “spread” across his pitches and matches the moderate movement on his Slider with similarly moderate (and opposite) movement on his 4-Seam Fastball, which he throws the other 20% of the time.
Ultimately, there is no one way to throw a Slider, and no single recipe for how to make it effective at high usage rates. That said, I don’t think it’s insignificant that Wisler’s “Goldilocks” slider is having similar success at the highest usage rate, potentially signalling a reduction in dependence on the rest of your arsenal. If each guy had to throw their Slider 100% of the time, I might put my money on Wisler’s despite its subjectively less impressive movement and spin characteristics. An important takeaway in my mind is the necessity of balance in a pitcher’s arsenal, and the more extreme a pitch becomes, the more important it is to balance its movement with an “opposite” pitch to stay deceptive and effective. I think Roe’s demonic Slider becomes easier to take if it’s thrown every time, and Garrett’s tighter Slider plays up off of his heater. I’m left then with a similar conclusion I had initially -- the success of a high-use breaking pitch is as dependent on the quality of the rest of the arsenal as it is on the pitch itself -- and even the most impressive pitches need the threat of another offering to keep hitters on their toes and generate whiff after whiff, year after year.
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