That did not occur to me. I will check that out. Thanks!

I just checked. There is a slight exacerbation with two strikes, but only slight. It's not strong evidence in favor of my hypothesis.

So what's going on here? I *think* I did the calculations correctly. Further investigation is required.

Perhaps batters are sometimes adjusting their swings just to make contact and foul the ball off. If so, we would expect to see this phenomenon exacerbated with two strikes ...

Let's compare batter results on their "fast" swings (above that batter's average bat speed) vs. their "slow" swings.

MLB avg (FB only, min. 50 comp. swings)

"fast" swings
84% contact
44% hit into play
31% squared up

"slow" swings
85% contact
34% hit into play
23% squared up

Conclusion: Let's exercise caution with our interpretations of swing length. It's probably true that longer swings lead to more swing-and-miss. But I need more convincing that the new data provide strong evidence in favor of this hypothesis.

When hitters are fooled by off-speed pitches, they start swinging early. The "point of contact" ends up out in front of the plate, increasing the measured swing length. Here, being fooled is correlated with both miss-swings and swing length. We see the opposite for fastballs.

What is going on with those long Cruz swings? Are they misses because they are long? Or are they long because they are misses? Here's the distribution of contact/miss swing length by pitch type. Miss-swings are longer for breaking balls and off-speed but shorter for fastballs!

Here is a comparison of Cruz's and Soto's swings. At the risk of making the figure too complicated, I also annotated contact/miss. The upshot is that Soto never takes swings > 8.5 feet like Cruz does, and these swings are almost always misses.

I wondered whether we could use this to measure swing adaptability: Which hitters are appropriately adapting their swings based on the pitch?

Standard Deviation in Swing Length (min. 150 swings)
#1 out of 186: Oneil Cruz (0.9 feet)
...
#186 out of 186: Juan Soto (0.5 feet)

This isn't unique to Cruz. It seems generally true across players. Players who swing hard tend to swing long. BUT for an individual player, swinging harder doesn't correlate strongly with swinging longer. I am curious what causes differences between swings for individual players.

By contrast, here is a visualization of within-player variance, specifically for Oneil Cruz. We see there is not much relationship between bat speed and swing length across Cruz's swings. Cruz doesn't seem to swing harder when swinging longer.

I'm particularly interested in comparing *between-player* variance in bat path and *within-player* variance in bat path. For example, here is between-player variance in bath path. We see that there is a correlation: Batters who swing hard tend to swing long.