The Junk Field Is Filled with Thriller

Each now and again, I take a peek on the Kirby Index leaderboards. In August, the anticipated names that populated the highest of the rankings: Kevin Gausman, Trevor Rogers, and Jacob deGrom. Equally, the underside featured stereotypically wild hurlers: Joe Boyle, Luis Gil, Freddy Peralta, and… Janson Junk???

In the event you’re accustomed to Junk, it’s most probably as a consequence of his wonderful command: Amongst all starters with not less than 70 innings pitched this season, his 3.0% stroll charge ranks because the lowest. (In a wonderful interview with David Laurila final month, Junk talked about coaching his command at Driveline over the winter.) Seeing Junk in final place on this leaderboard was like recognizing a polar bear in Arlington, Texas — in different phrases, an indication that one thing was critically amiss.

By all 4 parts of the Kirby Index, Junk ranked poorly. However his vertical launch level was significantly inconsistent, sitting useless final amongst pitchers within the pattern. In my article from final 12 months introducing the Kirby Index, which I linked to above, I discovered that the final word location of the pitch is dictated virtually totally by launch angles and launch factors. It follows that pitchers with inconsistent launch factors exhibit poor command. How was Junk various his launch level so steadily and nonetheless throwing so many strikes?

Paul Skenes isn’t the same pitcher, however he offered a possible reply. Skenes confirmed up close to the underside of authentic Kirby Index leaderboards as a result of he modified his place on the rubber relying on the handedness of the batter. In the end, that was a simple repair: By taking a look at fastballs thrown to right-handed hitters and left-handed hitters individually and averaging the outcomes, the rubber shifters could possibly be in comparison with the remainder of the pitching inhabitants.

Nevertheless, Junk wasn’t shifting across the rubber, and even when he was, it wouldn’t change his vertical launch level. However adjusting his arm angle would. Arm angle wasn’t publicly obtainable after I first wrote in regards to the Kirby Index, however it seems that for Junk, it explains the numerous variation in his vertical launch level in addition to his vertical launch angles.

From one pitch to the subsequent, Junk can change from a milquetoast three-quarters launch…

… to one of many extra excessive over-the-top arm angles within the league, touchdown someplace within the Jonah Tong/Trey Yesavage zone.

Right here’s the three-quarter nonetheless:

And the over-the-top one:

Amongst starters with not less than 300 fastballs thrown, solely Antonio Senzatela and Logan Allen featured extra arm angle variation on their four-seam fastballs.

Whereas I didn’t have entry to arm angle variation after I wrote that Kirby Index article, this funky Junk truth motivated me to see if this associated in any respect to the flexibility to command the ball. In brief: Apparently, under no circumstances!

To check this, I employed our two trusty fashions, Location+ and PitchingBot’s BotCMD, as proxies for command talent. I used the usual deviation of a pitcher’s four-seam fastball arm angle because the explanatory variable; for every respective mannequin, I used each the general grade (Location+ and botCMD) in addition to their fastball-specific fashions (botCMD FA, Loc+ FA) because the response variables. I restricted the pattern to pitchers with not less than 60 innings pitched and 300 fastballs thrown. Throughout all 4 combos of those explanatory and response variables, there was hardly a relationship.

OK, possibly in the event you squint, there’s one thing happening there with PitchingBot’s fastball command mannequin. However on the entire, there’s actually nothing there.

If arm angle variation doesn’t clarify command, it should clarify one thing, proper? In any case, there’s a robust and confirmed relationship between arm angle and induced vertical break:

Justin Willard, the Crimson Sox director of pitching, delivered a related quote in The Athletic’s lengthy article on induced vertical break revealed final week.

“Arm slot is the best correlated factor to spin course,” Willard stated. “Spin course is the best correlated factor to Magnus carry.”

However one thing else is occurring right here that’s type of shocking. When Junk’s four-seam fastballs are plotted towards their induced vertical break, it turns into clear that for him, particularly, the connection vanishes. Whether or not Junk throws from method over-the-top or from a normal three-quarters place, the quantity of vertical motion he will get on his fastball hardly varies.

It seems this phenomenon — whereas not as true for others as Junk — holds true throughout instances. Whereas the r-squared between arm angle and IVB on the pitch degree is 0.34, the averaged r-squared inside pitchers themselves is 0.05.

This felt like one other thriller in want of an evidence. How can the connection on the broader degree between IVB and arm angle be so robust, but clarify virtually nothing on the pitcher degree? I introduced this query to my pitching pal Stephen Sutton-Brown at Baseball Prospectus, who offered a compelling rationalization. On the particular person pitcher degree, arm angle and velocity stay (comparatively) fixed, and so the variation on any given fastball is defined extra by different components, like hand positioning or grip. On the pitcher inhabitants degree, the arm angle variation is, after all, a lot wider.

However Junk is a particular case. He does characteristic an honest quantity of arm angle variation, and so I anticipated some portion of his fastball motion to be defined by the adjustments in his arm place. It was not. Junk was one of many few pitchers with zero relationship in any respect between his arm angle and fastball vertical motion.

What’s going with this man? I wished to ask him. Sadly, the Marlins didn’t have the identical want; they declined to make him obtainable for an interview. For now, the mysteries of Junk will stay out of attain.