AFL PitchFX Pt. 1: James Simmons

As you all know, Major League Baseball runs a fall league in Arizona for upper-level minor-league players, appropriately named the Arizona Fall League. The big news this year is that, for the first time, MLB installed PitchFX cameras. This is huge—it’s the first PitchFX look we’ve ever gotten from minor-leaguers. I’m going to crunch the numbers and take a look at the results, hopefully churning out some useful scouting reports in the process. I’ll start with our 2007 first-round draft pick out of UC Riverside, James Simmons (RHP).

Okay, one caveat. MLB didn’t install PitchFX cameras in all of the Arizona stadiums. They unfortunately excluded Phoenix, the park that our A’s representatives call home. They did, however, install them in Surprise and Peoria, home of three of the six AFL teams, allowing the cameras to catch 10 of the 33 games our Phoenix Desert Dogs played. In Simmons’s case, I have data for only two of his appearances, for a total of 7.2 innings. It’s not much, but enough to build a scouting report on.

The problem with the PitchFX data I have is that the cameras caught two very different James Simmonses. The James Simmons that showed up on October 17th throws a 90-mph four-seam fastball, an 86-mph changeup with very little tailing action, and a 79-mph curveball that comes into left-handed batters more than it drops. The James Simmons of October 29th throws an 86-mph fastball that acts like a two-seamer which darts inside to right-handed batters, a 79-mph changeup that tails quite a bit (it matches his two-seamer), and a 67-mph curveball, identical to Simmons the First’s curveball in movement, but slower. Here’s a combined movement chart. These are all from the catcher’s point of view, by the way.


And here’s the same chart, broken down by game to emphasize the difference in movement.


Simmons achieved this big change in movement by lowering his release point by an entire 1.8 feet.


It was reported that James Simmons was testing out a cutter, and the graphs show that. Unfortunately, it seems to have extremely little lateral motion, and he only threw it six times in the games that PitchFX caught.

Of course, there’s always the possibility that the change was caused by imprecise cameras, as the two games were recorded at different parks (10/17 at Surprise, 10/29 at Peoria). Thankfully, another pitcher, A's prospect Sam Demel, pitched alongside Simmons on both occasions. If the difference in movement was an error in detection, Demel’s pitches and release point should have changed as well. They didn’t.


The AFL is a league for trying out new pitches and techniques, and it looks like Simmons used Arizona for that precise purpose. The sample size is obviously far too small to judge whether or not the new release point was effective or not, but it looks like Simmons will have 2010 to decide on a release point, and whether trading his already low velocity for extra movement is worth it.


Odds and Ends:

  • I generated a couple other charts if you guys want them. This one is velocity and lateral movement, and this one is velocity and vertical movement.
  • I also wanted to try something a little different, so I plotted spin angle vs. spin rate on polar coordinates. After wrestling with Excel for a long time, it turns out that polar graphs are impossible. So I converted the polar coordinates to rectangular coordinates—you're going to have to imagine the rest. The distance from the origin indicates spin rate, and the spin angle is denoted by the placement angle on the graph. Each hash mark on the axes is 1000 revolutions per minute. Oh, and unfortunately, the axes and their scales aren't equal. Thanks, Excel.
  • The huge change in release point confused PitchFX as well. It labeled all of the changeups that Simmons threw on the 29th as sliders. I'm not sure where the system got that result from, as that would make his supposed slider come into right-handed batters. An odd screwball, basically. I just relabeled them as changeups.
  • Any ideas for future PitchFX analyses are definitely welcomed. I had a lot to say about James Simmons, but I expect to have less material for the other players we sent to Arizona. Any other ideas of what to do with the data would be great.
  • Update: Hey, front page. Cool! Thanks, whoever you are.
Log In Sign Up

Log In Sign Up

Forgot password?

We'll email you a reset link.

If you signed up using a 3rd party account like Facebook or Twitter, please login with it instead.

Forgot password?

Try another email?

Almost done,

By becoming a registered user, you are also agreeing to our Terms and confirming that you have read our Privacy Policy.

Join Athletics Nation

You must be a member of Athletics Nation to participate.

We have our own Community Guidelines at Athletics Nation. You should read them.

Join Athletics Nation

You must be a member of Athletics Nation to participate.

We have our own Community Guidelines at Athletics Nation. You should read them.




Choose an available username to complete sign up.

In order to provide our users with a better overall experience, we ask for more information from Facebook when using it to login so that we can learn more about our audience and provide you with the best possible experience. We do not store specific user data and the sharing of it is not required to login with Facebook.