Exceptional Defense Touches Everyone

Here’s something that should be pretty evident: If you’ve got a ground-ball pitcher, you want him pitching in front of a strong infield defense. Likewise, if you’ve got a fly-ball pitcher, you want him pitching in front of a strong outfield defense. I feel like I don’t even need to explain the thought processes. How many times did people express concern over Rick Porcello starting for last year’s Detroit Tigers? Porcello’s a ground ball guy. Last year’s Tigers started Miguel Cabrera and Prince Fielder at the corners. Intuitively, that could’ve been a problem.

OK. As presented on FanGraphs, the UZR era stretches back to 2002. Over that span, last year’s Tampa Bay Rays had one of the best infield defenses, at +50 runs. Not surprisingly, ground-baller Alex Cobb posted an ERA well below his FIP. More surprisingly, fly-baller Matt Moore showed an even bigger positive difference. Let’s flip things around. The 2004 New York Yankees had one of the worst outfield defenses, at -68 runs. Not surprisingly, fly-baller Javier Vazquez pitched below his peripherals. More surprisingly, ground-baller Jon Lieber showed an even bigger negative difference. These are just carefully selected individual examples, but they help to set up a bigger-picture study.

Here’s the handwritten note on my notepad, from a few nights ago:

GB pitchers and great/bad infields

It started with me wanting to know how ground-ball pitchers have been affected by pitching in front of great infields and lousy infields. That turned out to be just the first step, as the study grew from there. It only made sense to examine all four of the following:

  • Ground-ball pitchers in front of good/average/bad infields
  • Fly-ball pitchers in front of good/average/bad infields
  • Ground-ball pitchers in front of good/average/bad outfields
  • Fly-ball pitchers in front of good/average/bad outfields

We can all guess the results, but we might as well get the actual numbers. So I went after the actual numbers, looking at data covering the past dozen years. I got information for a whole bunch of teams, and I got information for a whole bunch of players.

I generated a spreadsheet that included every pitcher season with at least 100 innings. I deleted those pitchers who were moved midseason, which left me with a sample of 1,578. For each pitcher season, I calculated a z-score for the ground-ball rate. I defined ground-ball pitchers as guys whose ground-ball rates were at least one standard deviation above the mean. I defined fly-ball pitchers as guys whose ground-ball rates were at least one standard deviation below the mean.

The next step was pairing players with corresponding team defenses, split into infield and outfield. I messed around with z-scores a little bit more. I defined a good infield or outfield defense as a unit that was at least one standard deviation above the mean. I defined a bad infield or outfield defense as a unit that was at least one standard deviation below the mean. For infields, one standard deviation was 21.4 runs. For outfields, one standard deviation was a nearly identical 22.5 runs. All the other defenses, by the way, were included in the “average” group. So this is an examination of groundball pitchers and fly-ball pitchers with good infields, average infields, bad infields, good outfields, average outfields and bad outfields.

I know this probably seems like a lot. The results make it out to be a lot simpler. There are going to be four tables, and here’s the first of them. This is data for ground-ball pitchers, with various infield defenses.

Inf. Defense WAR/200 RA9/200 ERA- FIP- BABIP Infield, z Outfield, z
Best 2.6 3.4 90 95 0.285 1.4 0.0
Average 2.7 3.0 93 95 0.293 -0.1 -0.2
Worst 2.7 2.1 100 96 0.303 -1.4 -0.3

To walk you through real quick — groundball pitchers in front of the best infield defenses averaged 2.6 WAR per 200 innings. They averaged 3.4 RA9-WAR per 200 innings. They averaged an ERA- five points lower than their FIP-, and they posted a .285 average BABIP. The best infields were an average of 1.4 standard deviations above the mean, in UZR. Those same teams also had average outfields.

Nothing about this table should be surprising. Ground-ball pitchers in front of good infields allowed a BABIP 18 points lower than ground-ball pitchers in front of bad infields. The good-infield group outpaced its WAR/200 by 0.8, while the bad-infield group undershot its WAR/200 by 0.6. The message: ground-ball pitchers benefit from guys who are better at dealing with ground balls. Of course.

But now let’s look at fly-ball pitchers, with various infield defenses.

Inf. Defense WAR/200 RA9/200 ERA- FIP- BABIP Infield, z Outfield, z
Best 2.4 2.9 97 103 0.276 1.4 0.4
Average 2.1 2.1 105 106 0.285 -0.1 0.2
Worst 1.9 1.4 110 108 0.289 -1.6 0.0

Even though you expect ground-ball pitchers to benefit the most from having a good infield defense, it’s not like fly-ball pitchers are left untouched. The good-infield group here outpaced its WAR/200 by 0.5, while the bad-infield group undershot its WAR/200 by 0.5. There’s a 13-point spread in BABIP. You can’t ignore the last column; there’s a small outfielder effect, here. But it’s mostly about the infield. Fly-ball pitchers also benefit, sometimes rather significantly, from guys who are better at dealing with ground balls.

Now to the third table. This is data for ground-ball pitchers, with various outfield defenses.

Outf. Defense WAR/200 RA9/200 ERA- FIP- BABIP Infield, z Outfield, z
Best 2.8 3.1 92 93 0.292 -0.2 1.6
Average 2.6 2.8 95 96 0.293 -0.1 -0.1
Worst 3.1 2.9 94 92 0.301 -0.5 -1.4

The good-outfield group here outpaced its WAR/200 by 0.3, while the bad-outfield group undershot its WAR/200 by 0.2. There’s an eight-point BABIP spread. Clearly, groundball pitchers derive a bigger benefit from a good infield than from a good outfield, but a good outfield does still help. A really good outfield can help by maybe half of a win.

Now for the last table: fly-ball pitchers, with various outfield defenses.

Outf. Defense WAR/200 RA9/200 ERA- FIP- BABIP Infield, z Outfield, z
Best 2.1 2.6 99 106 0.278 0.2 1.5
Average 2.2 2.1 104 105 0.284 0.1 0.1
Worst 2.1 1.7 108 107 0.287 -0.2 -1.3

The good-outfield group here outpaced its WAR/200 by 0.5, while the bad-outfield group undershot its WAR/200 by 0.4. There’s a nine-point BABIP spread. Obviously, fly-ball pitchers have gotten some help from good fly-ball catchers. But here something interesting: At least based on this evidence, fly-ball pitchers have been helped or hurt as much by the infields as by the outfields. Also interesting: At least based on this evidence, ground-ball pitchers have been helped more by good infields, relative to bad, than fly-ball pitchers have been helped by good outfields, relative to bad. It could be that I’m seeing something that isn’t there. It could be this would all go away with bigger sample sizes. For the moment, it’s something to think about.

And that’s maybe getting a little too particular. Here’s the most general point: Don’t forget that ground-ball pitchers allow balls in play in the air. Don’t forget that fly-ball pitchers allow balls in play on the ground. When you have a ground-ball guy or a fly-ball guy, it’s easy to pretend they only allow one thing. But infields don’t make a difference only for ground-ball guys, and outfields don’t make a difference only for fly-ball guys. If you’ve got a great infield or a lousy outfield, everyone’s going to feel it. After all this information, it seems so obvious. It is obvious. But defense matters, for everybody — always. It doesn’t matter the pitcher’s specialty, or the defense’s.



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Jeff made Lookout Landing a thing, but he does not still write there about the Mariners. He does write here, sometimes about the Mariners, but usually not.


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