Introducing Fastball+

A Super Simple Way to Estimate Fastball Quality

Have you ever wanted to calculate a rough estimate of how good a pitcher’s 4-seam fastball is, but don’t want to go through the hassle of getting data, preparing data and then training said data? I’ve got a solution for you that will allow you to get a pretty good estimate of a 4-seamer’s quality using only 4 ingredients: release height, release width, velocity and induced vertical break (IVB). Depending on where you’re getting your data from, you might need to calculate IVB yourself.

Let’s begin with a simple chart of just four seam fastballs from 2021-2023, split by release height and side.

Here we’re showing Induced Vertical Break per Flight (IVB/F) split by release point (release height in inches on the y axis, and release side on the x axis). We see a clear downward trend the farther away from your body you go as well as a clear downward trend the lower you release the ball.

The number in the box is basically what a batter expects to see given the arm slot. If we’re to model this, we can come up with a Net IVB, or the amount of IVB greater or less than what the batter would expect given the release point.

NET IVB = IVB - 7 + 1.0 * ABS(x0) - 1.9 * z0

I got those numbers using a simple ordinary least squares regression in Excel. It means that a pitcher’s expected IVB decreases by about an inch for every foot of release side and increases by about 2 inches per foot of release height. This is why being able to get even 16-17 inches of IVB at a super low release point can be extremely effective.

Once you have IVB, you can estimate fastball quality with this formula:

Fastball+ = 100 + 3.85 * Net IVB + 5.3 * (Pitch Velo - 95)

That’s it! Basically, 3 inches of Net IVB is worth about 10 points and every 2 MPH is worth about 10 points. Is this true in practice? Test it out and let me know! We could probably make this more accurate by using the actual release points (not the “0” release points), but I wanted to give you a formula with the most readily available components.

Fastball+

There’s beauty in simplicity. Here are the top 2024 names, min 100 pitches:

And the best 2024 fastballs min 1000 pitches:

Definitely passes the eye test!

Conclusion

Please test it out. It should work for any pitcher where you have the 4 ingredients. Let me know what you discover and if you find a better version.