Brian Bannister Looks at His PITCHf/x Numbers

Over the weekend Tom Tango linked an interview Brian Bannister did talking about how he used PITCH/x information to change his approach this year. It is a really interesting interview that I urge you to listen to. This morning Harry Pavlidis posted a great breakdown of the things Bannister talked about. I wanted to expand on a couple of things Harry looked at.

As some of you might know Bannister is a student of sabremetrics. Back in 2007 when he had a great ERA, build largely on a unsustainably low BABIP, he understood what was happening and that his current approach would not work going forward. In the interview he talked about going into 2008 looking to increase his strikeout rate to decrease his FIP. To do so he tried to work on his four-seam fastball. As we know it didn’t work. His strikeouts didn’t increase, his BABIP regressed and he had a very poor 2009. So going into 2009 he realized the other way to increase his FIP would be to increase his GB rate and thus decrease his HRs. So going into 2009 he wanted to stop using his four-seam fastball as much and replace it with a cutter that he had throw in the minors but given up. The cutter has less ‘rise’ and gets more ground balls. He also talked about changing the grip on his changeup to throw a power change, which results in a changeup with less ‘rise’ and thus get more ground balls.

I wanted to look at this change in approach of replacing his four-seam fastball with a cutter as his main pitch and the change in his changeup. First I went through and reclassified his pitches for this year and last year since both BIS and PITCHf/x are mislabeling his cutter.

```+--------------------+-------+-------+
|                    |  2008 |  2009 |
+--------------------+-------+-------+
| Four-Seam Fastball |  0.58 |  0.23 |
| Cutter/Slider      |  0.20 |  0.51 |
| Changeup           |  0.13 |  0.16 |
| Curveball          |  0.09 |  0.10 |
+--------------------+-------+-------+
```

I had a hard time telling the difference between his cutter and slider. To the best of my understanding I think in 2008 most of those are sliders and in 2009 mostly cutters. So the big difference is in exchanging his main pitch from a four-seam fastball to a cutter, just as Bannister said in the interview. Here is a comparison of his 2008 four-seam fastball to his 2009 cutter to see the results of this shift.

```+--------------------+-------+-------+-------+-------+
|                    |  zone | whiff | oswing| GB/BIP|
+--------------------+-------+-------+-------+-------+
| Four-Seam Fastball |  0.59 |  0.11 |  0.20 |  0.30 |
| Cutter             |  0.58 |  0.10 |  0.24 |  0.47 |
+--------------------+-------+-------+-------+-------+

```

It looks like he can hit the zone and get whiffs and out-of-zone-swings at roughly the same rate with his cutter that he did with his four-seam fastball, but it gets about half again as many ground balls. That is an exchange anyone would be happy to make.

Bannister also mentioned his new power change that is a little faster has less rise, or vertical movement.

It is working, the GB rate on his change has risen from just under 50% last year to 69% this year.

Overall Bannister’s transition has been great. He is striking out and walking about the same number of hitters, but instead of being a 40% GB pitcher he is a 48% GB pitcher. That is a huge difference, which should result in many fewer HRs and probably make him a league average pitcher.

I think this is really cool. Bannister looked at his stats, understood something had to change, went about changing it and so far it looks like it has worked. I am very happy for him.

Dave Allen's other baseball work can be found at Baseball Analysts.