It’s been a fun couple of weeks seeing all the work that has been done as a result of Statcast’s expanding into bat tracking. The great thing about this game is that there is always more to learn. With the addition of bat speed and swing length, we now have a better idea of telling the story of a player’s swing, but there is still so much more to tap into.

Back when I was using a Blast Motion bat sensor on a daily basis, I was exposed to every component of the swing that you could think of. Bat speed was one of them, but that only scratched the surface. There were pieces explaining my path at different points in the swing, how long it took my barrel to meet the plane of the ball, where in space that happened, and so much more. For a while, the public data available was focused on the outcome. What was the pitch? What was the result? What was the exit velocity and/or launch angle? With this new update, we’re progressing toward the how. How fast did the player swing? How long was their swing? We can now tie that in with the result, but there are additional details needed to understand the full scope of how results happened. That’ll be the focus of this piece.

First, it’s important to highlight the great work that has already been done explaining the new data we have and what the information tells (and doesn’t tell) us about the swing. Ben Clemens explained some applications of the new metrics and what their relationship with performance is on a macro scale. One thing Ben mentioned that resonated with me is thinking about the new (and old) information as inputs for us to use to understand performance rather than the answers themselves. Each piece works together to tell a story, whether that be league wide or player specific. Basically, these are pieces of information that need additional context.

Relatedly, Patrick Dubuque and Stephen Sutton-Brown from Baseball Prospectus, provided a great analysis of how to put bat speed into the context of pitch counts, from the perspective of both the hitter and pitcher. And there is more beyond just these two, including Noah Woodward’s Substack post about bat speed, swing length, and understanding what they mean and how they contribute to the swing.

Woodward touched on a few components of the swing that I’ve talked about in previous work that we still don’t have comprehensive data on from Statcast: contact point and attack angle. Swing variability, swing adjustability, having A and B swings, etc. are all extremely important to being successful at the big league level. If you have a hole in your swing, generally speaking, pitchers will expose you, so having multiple high-quality swings is going to set you up to have consistent success, just ask Triston Casas. Swing-by-swing data on attack angle, vertical and horizontal bat angle, and point of contact will all help the public understanding of swing variability, or when and how the swing changes in general.

Let’s start with attack angle. This is the angle of the bat path at contact, relative to the ground. As your bat travels through the zone, it creates a trajectory. To optimize your chances of hitting the ball in the air, the bat should be on an upward trajectory at contact, meaning you should have a positive attack angle. One component of swing variability is creating a positive attack angle at different heights, widths, and depths. You pretty much just want to be able to manipulate your barrel to move upward no matter where the pitch is. To get a better idea of what attack angle looks like, let’s look at a video from David Adler outlining a swing from Oneil Cruz:

Bat path tracking — Oneil Cruz 120.4 mph single (hardest-hit ball in MLB this year)

84.5 mph bat speed (75+ mph is the "fast swing" threshold) pic.twitter.com/FO9gA6fqva

— David Adler (@_dadler) May 21, 2024

While attack angle is officially measured as the angle of the path at contact, seeing the path leading up to contact can tell us what kind of depth the hitter creates. In this clip, the angle of the path changes as it moves from behind Cruz’s body to in front of it. This illuminates how attack angle is dependent on point of contact. In general, the farther in front of the plate your bat is, the easier it is to create a positive attack angle. However, this thread from Driveline’s Director of Hitting, Tanner Stokey, discusses the importance of creating bat speed deep in the zone. The best hitters create their peak speeds in tight windows. Like all facets of baseball, swinging is about striking a balance of creating high levels of bat speed and positive attack angles. You don’t want to have a one dimensional swing that is focused on high bat speed while ignoring the need to create ideal bat angles both deep in the zone and in front of the plate.

Depending on how you start your swing and enter the zone, it takes time to turn your barrel over into an upward slope. For many hitters, the bat needs to travel a greater distance to create the positive attack angle that leads to optimal contact. This, of course, takes more time. But, as Robert Orr pointed out last week in his piece on the relationship between pulled fly balls and swing length, a long swing isn’t necessarily a bad thing; it’s really just another data point. With access to attack angle, we could better tell the story of how a hitter like Isaac Paredes creates depth in his swing while often making ideal contact far out in front of the plate, versus a hitter who makes contact out in front without creating the necessary depth in their swing to avoid major holes.

At the same time, it’s still possible to create a positive attack angle deeper in the hitting zone. To get there, you need to make movements that aren’t easy to do while generating bat speed and controlling your body. Some hitters with great mobility use lateral torso bend — they lean toward their back leg right before contact — to get their barrel on an upward slope deep in the hitting zone. Think of Shohei Ohtani or Edouard Julien:

These two have unorthodox skills that allow them to launch pitches high in the air to the opposite field. With point of contact and attack angle, we’d be able to quantify how different they really are from their peers on top of the visual analysis.

Then there are hitters who create flatter (but still positive) attack angles with a path that stays on a similar plane throughout their swing. They get on plane with the ball early and don’t do much to change their path throughout the swing. It’s nearly impossible to do this with a steep swing. Juan Soto is a great example of this, even if he is more powerful than the other hitters with this swing style. Here is a great angle that illustrates what I’m referencing:

Bat path tracking — Juan Soto 112.0 mph line-drive single off Justin Verlander

Staying on top of a hanging curveball at the top of the zone pic.twitter.com/IRhdzHVMy8

— David Adler (@_dadler) May 8, 2024

Soto’s vertical entry angle (angle of the bat relative to the ground at the beginning of the downswing) isn’t far off from his attack angle. You can see how much this swing contrasts with that of Cruz, who is a big dude with a narrow stance. Because of that, his bat path is vertically oriented, and his bat needs to travel a greater distance to get on plane with the ball. With more detailed information of barrel angles at different points in the swing, we would know more about how hitters like Soto and Cruz vary from one another when it comes to getting and staying on plane.

This has been a ton of information all at once, so I’ll leave you with one last tidbit. Depending on the hitter, the angle of the path at contact can be very different from the angle of the barrel at contact (relative to the ground), known as vertical bat angle. While I’ve cited average vertical bat angle from SwingGraphs on several occasions, I’ve always focused on putting the metric into context because it varies based on several factors. Luis Arraez and Aaron Judge can have similar average vertical bat angles, but that doesn’t tell us anything about how different their swings are. We know the metric depends on pitch height, but even that alone isn’t enough to explain why Judge is a launcher and Arraez is a sprayer. As we learned earlier, each data point is an input and isn’t meant to be used alone.

There is no question teams have been using, monitoring, and applying these data to scout and develop players for years now, but despite all the metrics that we have, the information on the public side is still lagging. Ideally, in future years, we will gain access to more swing data so that we can better understand the game we love.

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