A pitcher’s swinging strike rate is one of the better measures of how well they are performing. It correlates well to their overall strikeout rate, and is one of the three gold standards I use (along with other methods) to evaluate a pitcher as a whole, in conjunction with O-Swing% (how often a hitter chases) and Z-Contact% (how little hitters make contact with pitches in the zone).

SwStr% can be used to inspect the effectiveness of either an entire arsenal or an individual pitch, and is a strong indicator of how good a pitcher’s “stuff” is. As such, an increased SwStr% is a desirable outcome for a pitcher. Obviously, some pitching styles don’t lend themselves to missing bats, and instead are good for timing disruption and/or weak contact.

One pitcher who fits the mold of a bat-misser is the young lefty prospect from the Oakland Athletics, Jesus Luzardo.

With a minuscule sample of just six games in 2019, amounting to 12 innings pitched, Luzardo had a strikeout rate of 34% (versus a 6.5% walk rate), and held hitters to a .119 batting average with an 0.67 WHIP while posting a 2.36 FIP (1.50 ERA). Luzardo was pretty good during the American League Wild Card game as well. Back in October against the Tampa Bay Rays, he pitched three innings, allowing one hit and two walks while striking out four.

It was a great start to Luzardo’s young career. As we know, these stats take time to stabilize, but they may be a strong indicator of what’s to come. According to our own Eric Longenhagen:

Luzardo has upper-90s gas, perhaps the best slider (sic) in the minors, and impressive command for someone with such a high-effort delivery. He’s a front-end arm with heightened injury risk.

Luzardo has four pitches in his repertoire. He has two versions of his fastball; both are sinkers by nature, but one tends to become more of a copycat version with a heavier backspin component. His “true” sinker features what Longenhagen calls “barrel-shattering tail”, with a decent amount of drop:

Luzardo also has a frighteningly effective breaking ball in his gyro-heavy slurve:

And Luzardo has a changeup that’s a pretty good pitch as well. It’s a fader that spins about 40 minutes (9:20) above his fastball (10:00), with just a small degree of gyro applied:

All three offerings from the A’s lefty are considered plus pitches, which Luzardo has above-average command of. However, in this particular case, it’s his sinking fastball and slurve that we’ll be paying attention to as I attempt to improve the efficacy of his SwStr%.

Earlier this month, a trio made up of former FanGraphs writer Eno Sarris, Southern Methodist University Associate Professor in Electrical & Computer Engineering Joe Camp, and Wake Forest University mathematical business major Gregory Dvorocsik presented research (which you can watch here) identifying pitch subtypes and what pairings they found to be most effective. Using data from the 2016-2017 season, they looked at each pairing’s impact on SwStr%, exit velocity, and launch angle.

They inspected the most common pitches (fastballs/sinkers, curveball/knuckle curve, changeups, splitters, sliders, cutters) and broke them down into scaled sub-categories (ex: SI1, SI2, SI3) based upon horizontal and vertical break, velocity, and spin rate. After coming up with around 30 subtypes, they looked at each in isolation based on the aforementioned criteria. From there, they paired each subtype to see if the pair improved or degraded from its standalone performance.

For example, let’s say a pitcher had a four-seam fastball that was deemed an “FF2” based on its movement profile along with velocity and spin rate compared to the average for each fastball subtype. The trio looked at all the other options to pair with that pitch to see which combination was the best and worst, in terms of the measured data when paired with the fastball.

Since we are focusing solely on Luzardo and swinging strike rate for this investigation, let’s first examine the best combinations to facilitate that. Observe the three best tandems for left-handed pitchers for SwStr%:

Most Effective Pitch Parings, SwStr%

+4.2 SwStr% Velo Spin Rate H-Mov V-Mov
CU3 75 2550 -2.4 -3.7
SI3 91 2083 9.6 5.8
KC2 78 2350 -3.6 -4.4
SL2 86 2326 -1.2 4.0
FT3 92 2132 9.7 7.3
SI3 91 2083 9.6 5.8

SOURCE: MLB Advanced Media

Luzardo, who throws both a sinker and a curve/slurve, matches our top SwStr% data almost perfectly with a couple of exceptions. Both his sinker and slurve are thrown harder, while his slurve matches much more closely than his sinker does in terms of average spin rate. That matters a bit less than the actual shape each average subtype produces.

For Luzardo’s slurve, the movement profile matches up pretty well. His sinker is identical in terms of ride, but it drops exactly one inch further than the average SI3. (Keep in mind that we aren’t privy to the standard deviation of each pitch subtype’s data.)

Jesus Luzardo 2019 Subtype Data

Subtype Velo Spin Rate H-Mov V-Mov
Sinker (SI3) 96 2290 9.6 4.8
Slurve (CU3) 83 2483 -2.6 -3.3

SOURCE: MLB Advanced Media

Knowing how well Luzardo’s sinker and slurve match the average shape of their respective subtypes, I parsed his pitch sequence data to find results from throwing a sinker to slurve or slurve to sinker during each at-bat. Of the 27 times Luzardo threw each pair, he drew a 33% strike rate (fouls, whiffs, called strikes) and a 15% SwStr-rate.

I’d venture to guess that if Luzardo can throw this pairing more often, he could potentially increase his SwStr% from 15% to around 19-20%. This would also be contingent on him getting his sinker closer to the average movement profile of sinker subtype number three.

To do that, we will have to make a minor tweak or two. Let’s use the Driveline Baseball EDGE tool to inspect his current sinker and see what changes he’d be expected to make with a change to its design.

In 2019, Luzardo’s sinker was thrown with 98% spin efficiency and a spin direction of 10:00 on average (or about 120-degrees). I’ve used the EDGE tool to see if I can produce an extra inch of lift while sacrificing minimal run. Note that the way this tool measures movement is a bit different than the movement data presented in the original research. I believe it’s a fair estimate to scale the two in regards to adding/subtracting movement.

I’ve found that adding around 15 more minutes to Luzardo’s spin direction produced the desired results. That’s certainly feasible for Luzardo, as based on the research by Dan Aucoin of Driveline, the standard spin direction deviation under a given arm slot for sinkers is about 20 minutes (or 11-degrees). I also accounted for the slight change by adding about two degrees of gyro tilt that could (at least theoretically) be created, thereby causing a slight decrease in spin efficiency:

It might not seem as though a pitch that lifts an extra inch can change much. The graphic below from this article posted by Driveline back in 2016 shows the effect of increasing/decreasing spin rate. However, I’m using it to demonstrate how an inch or so of movement can impact the type of contact a hitter is able to produce. Look at the area I’ve circled; you can see that in some cases, it can be the difference between a fly ball and a foul tip or popup:

Luzardo already has strong whiff numbers, although a full season’s worth of work would help to solidify that statement. Based on the research presented by Sarris, Camp, and Dvorocsik (which will be publicly available next month in the SABR Research Journal), Luzardo can get even better if he can make some minor changes to his sinker. Adding an additional 15 minutes of spin direction (or about 8 degrees) to the sinker will create the type of movement that could enable Luzardo to be an even better pitcher than scouts and prospect evaluators are already projecting him to be.

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