Earlier this week, I wrote about Emmanuel Clase. Particularly, I questioned whether or not a decrease launch level, or no matter brought on that decrease launch level, was the explanation his efficiency took a step again in 2023. I don’t know the reply for certain. I don’t even suppose there’s a solution to know the reply for certain, however I’ve spent the previous few days excited about launch factors. Clase’s has fallen roughly two inches during the last two years. That appears like lots to me, however I understand that I don’t have a foundation for that feeling. What occurs to a pitcher’s launch level on a year-over-year foundation? Does it keep the identical? What constitutes a traditional quantity of variance? Does it solely fall off as soon as issues are beginning to go unsuitable? Does it slowly degrade over time identical to the pitcher himself, who’s in any case merely an ephemeral vessel of bone and sinew, destined to return unto the mud?
Naturally, there’s just one place to search out solutions for metaphysical questions like these: Baseball Savant. I pulled the typical vertical launch level for each pitcher within the Statcast period, calculating the year-over-year change for his or her major fastball. For pitchers who threw each a four-seamer and a sinker, I ignored whichever pitch they threw much less usually. I additionally threw out seasons wherein gamers modified their launch level by greater than 4 inches, which to me signifies an intentional change to a pitcher’s supply and general method to pitching. We’re taken with instances like Clase’s, the place his launch level modified unintentionally as he tried to pitch in the identical means.
That left me with a goodly pattern of 5,353 participant seasons. Along with calculating the change in vertical launch level, I additionally famous the change in fastball velocity, together with the adjustments within the pitcher’s general FIP-, whiff charge, and groundball charge (adjusted to league common). The very first thing I did was create an growing old curve, however earlier than I present it to you, I’d wish to let you know what I used to be anticipating to see.
Moving into, my hunch was that launch level would fall steadily over time. Not solely that, however I anticipated that few gamers would see their launch level tick up from one yr to the subsequent. This speculation was partly knowledgeable by my very own private experiences as an (extraordinarily) beginner pitcher, however it additionally appeared like frequent sense.
Per Joshua H. Lam and Bruno Bordoni, “The first muscular tissues concerned within the motion of arm abduction embrace the supraspinatus, deltoid, trapezius, and serratus anterior.” You may recall that Wade Miley is coping with a strained posterior serratus proper now and that Andrés Muñoz hit the IL with a deltoid pressure again in April. Whereas there wasn’t a documented trapezius damage in 2023, pitchers Lance Lynn, Kyle Zimmer, and Justin Anderson all suffered trapezius strains over the previous few years. The supraspinatus is part of the rotator cuff, and the listing of pitchers who’ve suffered rotator cuff accidents is lengthy certainly. In different phrases, pitching is thought to create put on and tear on each single one of many major muscular tissues concerned in elevating the arm. It is sensible that it’d have an effect on one’s skill to take action, even for these fortunate sufficient to keep away from main damage. And that’s earlier than accounting for the conventional results of growing old, akin to decreased flexibility. With that, right here’s our growing old curve:
That may be very definitive. Launch level tends to fall over time. Even in the event you don’t belief the perimeters of the graph, the typical pitcher’s launch level drops by greater than 1.5 inches between the ages of 24 and 34. As with every growing old curve, it’s vital to remember the fact that there’s some severe survivorship bias happening right here. Pitchers whose launch level fell from one yr to the subsequent typically threw barely fewer pitches within the second yr, considerably minimizing their influence on the curve.
Possibly essentially the most attention-grabbing a part of all this information is the distribution. The common pitcher’s launch level falls by simply 0.13 inches per season, and the usual deviation is a surprisingly massive 1.5 inches. Right here’s what that appears like in graph kind, placing all year-over-year adjustments into buckets of 0.5 inches:
In a given yr, 51.6% of pitchers see their launch level drop, whereas 45.2% see a acquire. Whereas the general development is down, it actually may be very slight, and a pitcher is almost as more likely to increase their launch level as they’re to decrease it. A year-over-year drop of an inch, like Emmanuel Clase’s, is in one thing just like the 73rd percentile. It’s a big drop, however under no circumstances huge (although when it occurs for 2 consecutive years, it’s positively slightly extra worrisome).
The very last thing I did was run some correlation coefficients, utilizing fastball velocity as one thing like a management variable:
Vertical Launch Level and Efficiency Correlations
| Issue | Vert RP | FB Velo | FIP- | Whiff% | GB%+ |
|---|---|---|---|---|---|
| Vert RP | – | -.01 | -.01 | .01 | -.05 |
| FB Velo | -.01 | – | -.29 | .29 | .13 |
A rise in fastball velocity is correlated with a greater FIP, extra whiffs, and extra groundballs, simply as you’d anticipate. Even after accounting for the survivorship bias that I discussed earlier, I used to be a stunned to search out primarily no correlations between vertical launch level and, nicely, a lot of something (although as a result of launch level falls at roughly the identical charge as velocity, the correlation between the 2 may be understated). Nonetheless, I assumed that damage is no less than one of many causes a pitcher’s launch level may fall. As such, I anticipated a decrease launch level to be correlated with some drop-off in efficiency. As an alternative, the one correlation for which you might make any actual argument is groundball charge, presumably as a result of a decrease launch level means a shallower vertical method angle. I feel there’s plenty of room for extra examine, however as far as I can parse it, this information is telling us that even a drop on the order of an inch or two isn’t essentially a warning signal {that a} pitcher’s efficiency is about to fall off.
Many because of Dr. Paul Canavan, who took the time to introduce me to a number of the analysis on the biomechanical causes that older gamers might need decrease launch factors.