Cardinals AFL pitchers PITCHf/x data

Looking behind the numbers put up by Boone Whiting, Kevin Siegrist and Seth Blair in their final Arizona Fall League starts.

A little-publicized fact was that two of the spring training ballparks used in the Arizona Fall League this year have the PITCHf/x tracking system installed and operational. One of them is the home of the St. Louis Cardinals players competing, Surprise Stadium.

Throughout the AFL schedule,'s Gameday application included PITCHf/x data when available. While this is standard fare in the majors, getting the data for the minors in a consistent manner is uncommon. Yet the data was presented in its raw, pitch-by-pitch form.

When reviewing Boone Whiting's last start, made on Thursday, November 15, the final day of the AFL's regular season, I ended up combing through his PITCHf/x data. While doing so, I summarized it.

I was so interested that I went on to do the same thing for his teammates' final outings as well. Kevin Siegrist started three days earlier and Seth Blair two days prior to that, both at home, using the same equipment.

Two terms are important in understanding the data. They are BRK or break and PFX. The following explanations were adapted from

"BRK" is the greatest distance between the trajectory of the pitch at any point between the release point and the front of home plate, and the straight line path from the release point and the front of home plate.

"PFX" is the distance between the location of the actual pitch thrown over the plate, and the calculated location of a ball thrown by the pitcher in the same manner, but with no spin. In other words, this is the amount of "movement" by the pitch.

A faster, straighter pitch like a fastball will have a higher PFX value than a slower, breaking ball like a curveball, which will have a higher BRK value.

I also added the counts of each pitch thrown and the percentage of the starter's total that day. In each case, they were allowed to go about 70 pitches deep into the game.

Whiting 11/15 @Surprise
Pitch Velo BRK PFX # pitches % pitches
Fastball 87-92 2-4 10-15 35 49.3%
Change 75-81 7-10 9-14 29 40.8%
Slider 79-82 9-10 1-3 6 8.5%
Cutter 91 3 13 1 1.4%
Siegrist 11/12 @Surprise
Pitch Velo BRK PFX # pitches % pitches
Fastball 87-92 4-9 9-14 50 75.8%
Slider 72-76 11-14 2-6 11 16.7%
Change 78-83 9-10 9-12 5 7.6%
Blair 11/10 @Surprise
Pitch Velo BRK PFX # pitches % pitches
Fastball 91-95 (97) 3-6 10-15 49 70.0%
Curve 81-84 11-12 4-10 12 17.1%
Slider 82-84 9-11 5-7 6 8.6%
Change 80-81 6-8 9-11 3 4.3%

While Whiting and Siegrist's fastballs were all in the 87-92 mph range, Blair worked between 91-95, with one 97 mph offering. The PFX counts for all three were similar, though Siegrist's pitches had more break.

Whiting was the only one of the three to throw less than 70 percent fastballs – about half. He relied almost equally on a changeup that was as slow as 75 mph and had the most movement.

Siegrist's key secondary pitch was his slider, while Blair broke out his curve with about the same frequency, roughly 17 percent of the time. Blair also showed a slider and changeup in his outing.

Despite this interesting data, one should be careful not to draw firm conclusions from such a small number of pitches. One could easily go much further into the data. For example, I stopped short of digging into effectiveness of the pitches (balls and strikes) as well as strikes looking versus swinging, let alone reviewing multiple outings. Still, an interesting snapshot is provided.

Brian Walton can be reached via email at Also catch his Cardinals commentary daily at The Cardinal Nation blog. Follow Brian on Twitter.

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