Aaron Brooks' repertoire

By Jason Wojciechowski on August 2, 2015 at 1:47 PM

In at least three venues, I've compared Aaron Brooks to Brett Laxton. I've also said that if Brooks wanted to troll me hard, all he had to do was go out and pitch like a monster. Or, hell, a competent big-league pitcher. Seven and a third innings with five strikeouts, no walks, and one run later, I am trolled. He got me.1

Brooks threw five pitches last night: a two-seam and four-seam fastball (the latter more frequently), a better changeup than I thought he'd have, and both a slider and a curve (at least as far as Brooks Baseball/PitchInfo is concerned -- it's possible that A. Brooks considers these varieties of the same pitch, though the two pitches PitchInfo sees are substantially different in velocity and break). With the PITCHf/x data gathered from last night, let's throw some comps on those pitches.

Pitch Count Velocity HMov VMov Most comparable pitcher
Four-seam 41 93.1 -6.2 9.6 Anthony DeSclafani (93.5, -5.6, 9.7)
Two-seam 16 91.9 -8.1 6.6 Adam Warren (92.6, -8.1, 6.3)
Changeup 24 83.8 -8.2 2.7 Kyle Gibson (84.6, -8.3, 3.2)

I'm not going to do the exercise for the curveball and slider because he only threw 13 of them combined. The above samples aren't big enough to draw any firm conclusions either, but I think there's a difference between a fun exercise and a total farce. I'm trying to stay on the right side of that line.

There's a commonality here between Brooks and the three pitchers named in the table:

Pitcher Pitches Four-seam velo. 2015 DRA 2015 cFIP Career IP Career ERA-
DeSclafani 4s, 2s, sl, ch 93.6 3.91 108 153 114
Warren 4s, sl, ch, 2s, cu 93.4 3.57 110 255 86
Gibson 2s, sl, ch, fs 92.9 3.54 104 361 112

DRA is Baseball Prospectus' pitching metric, and it's expressed on the runs allowed (not earned runs) per nine scale. The league's RA/9 this season is 4.16, for the sake of comparison. cFIP is also a Baseball Prospectus statistic, a sort of adjusted version of FIP expressed on the "minus" scale, i.e. below 100 is better for a pitcher. ERA- is also on that scale.

If Brooks' arsenal is measured by his start yesterday, he has less breadth than the other three pitchers, as he was essentially a fastball-changeup guy; the others all have a slider they throw at least 20 percent of the time. Of course, we can't necessarily measure the arsenal by yesterday's start because the fastball and changeup were working so well that Brooks had no need to dip into the breaking ball(s) more than occasionally. (For what it's worth, if you include Brooks' prior major-league work, his slider usage jumps all the way to 12 percent.)

Overall, you could find ways to comp all three of the above pitchers' arsenals to Brooks', putting aside the issue of the breaking balls, but we can also nitpick those comps at a variety of levels:

  • DeScalafani's fastballs and changeup are probably the most similar to Brooks' on velocity and movement, but his changeup is a distant fourth place in terms of usage and comes in nearly 3 mph faster than Brooks'; given that their fastballs are essentially the same, that's 3 mph less separation between the fastball and changeup. There's no hard-and-fast rule about whether more or less separation between fastball and change is more effective (see Felix Hernandez, 4 mph gap, on one end and Johnny Cueto, 9 mph gap, on the other) -- Harry Pavlidis has found that big-gap changeups induce more whiffs and small-gap changeups more grounders -- but the gap is a key characteristic in a pitcher's arsenal that helps undermine a comparison.
  • Warren's sinker and changeup are quite similar to Brooks', but his four-seam fastball, his most-used pitch, has about half the horizontal movement of Brooks', a full three inches less.
  • Gibson's pitches are probably the best comp for Brooks', though he also has two inches less horizontal movement on his four-seam fastball; more importantly, his four-seam/sinker usage is essentially a mirror image of Brooks': 16.5%/42.5% vs. 43.6%/17.0%.

I'd say there are two takeaways here:

  1. Every player is different. Comps are impossible.
  2. Brooks probably has fourth/fifth starter upside.

  1. He also got me because it turns out I'd misremembered Laxton entirely. I thought he came to the A's with some more notable Royal in one of the A's many trades with Kansas City, but it turns out the opposite: Oakland drafted and developed him, then sent him to Missouri straight up for Jeremy Giambi.