How has Jason Heyward batted vs. lefthanded pitchers post-beaning?

Inspired by commentary from ESPN's Mark Simon while he was a guest on a radio show, we took a look on Saturday at whether getting beaned on August 21, 2013 by Jon Niese had impacted Jason Heyward's ability to handle inside pitches. That analysis looked at Heyward's pre- and post-beaning stats against all pitchers for two reasons: (1) The comparison included the largest number of pitches, swings, whiffs, and hits possible; and (2) It provides a point of comparison for analyzing Heyward's performance on inside pitches from lefties.

First, a reminder about sample size. Rather than the standard caveat, I want to stress the underlying meaning. There's a difference between analyzing stats that reflect performance and reaching a conclusion about a player's underlying skill. In a small enough sample, anything can happen. When looking at Heyward's performance on inside pitches from lefthanded pitchers post-beaning, we are dealing with samples of pitches, swings, whiffs, and at-bats that are quite small.

Once again, we are using the strike zone heat maps from the wonderful Brooks Baseball. As I explained in the initial post, keep in the mind that the color-coding is player specific. If a player is bad enough in every quadrant of the subdivided heat map, a .250 batting average could be red. If he is a good enough hitter, a .350 batting average might be blue. The player's relative heat in a given quadrant is relative to how he hits pitches elsewhere on the map, not MLB as a whole fares. Keep this in mind when evaluating how Heyward has performed on inside pitches from lefties.

Batting Average vs. LHP

This chart covers Heyward's career before the beaning he sustained on August 21, 2013.

Here's the heat map post-beanball.

I almost didn't include these two charts. They cover a tiny amount of pitches that Heyward put in play. To look at the color-coding, it's easy to conclude that Heyward's performance against lefties on inside pitches fell off, just as it did overall—Heyward posted a .169/.252/.225 (.225 wOBA, 39 wRC+) against southpaws in 2014. That line, which was put up over 159 plate appearances, isn't enough to draw any dependable conclusions about Heyward's talent for hitting lefties (more on this later in the week). So attempting to do the same based on Heyward's inside corner splits against lefties is a fool's errands. Sure, Heyward's BA has gone down, but it's over 11, 8, 8, and 5 at-bat samples. One more hit would drive his BA to an approximation (or well above) his career rate against inside pitches by lefties. In the end, I included these charts just to tell folks not to read too much—i.e., anything—into them.

Isolated Power vs. LHP

Unlike slugging percentage (SLG), which is calculated using singles, doubles, triples, and home runs, ISO is based only on extra-base hits. For this exercise, we're using it as a proxy for Heyward's quality of contact. We'll start with the Brooks Baseball ISO heat map covering the time period before Heyward was beaned.

Now, the Brooks Baseball ISO heat map for Heyward's post-beaning hits against lefties.

As with the BA charts, there are far too few at-bats shown on the ISO chart for there to be any statistically significant conclusion reached. You can take the fact that Heyward hit for more power on inside pitches from lefties after getting beaned than before for what it's worth: Not much.

Swing Rate vs. LHP

Swing Rate measures just what you think it does: How often a player swings at pitches in a given area of the strike zone (or, outside the strike zone). In this analysis, we're using Swing Rate as a proxy for aggressiveness. My thinking is that, if the beanball impacted Heyward's plate approach, it might show up in how often he swings at pitches on the inside part of the plate or off the plate and in. We'll start with his pre-beaning heat map.

For comparison, his post-beanball heat map.

While Heyward's Swing Rate has fallen off by a couple of percentage points in some areas of the zone, he also has been much more aggressive in swinging at inside pitches thrown by southpaws in other areas since the beaning. There's no indication that being struck in the face and suffering a broken jaw has made Heyward more tentative on inside pitches from southpaws. If anything, he's been more aggressive on portsider-thrown inside pitches post-beanball.

Whiff Per Swing vs. LHP

There are multiple ways to measure the rate at which a player swings and misses. At Fangraphs, they use Swinging Strike Rate (SwStr%) which measures the share of a player's strikes that are swings-and-misses. There's also whiff rate, which shows the share of swings-and-misses out of total pitches. Then there's Whiffs Per Swing, which shows just what its name suggests. That's what we're going to use for this exercise. Here's the heat map covering the time period from Heyward's rookie debut through August 21, 2013.

Now the post-beanball heat map.

Again: Small. Sample. Size. There's really nothing to see here. It isn't so much better or worse than before the beaning, that it causes one to wonder about a change. Their size makes the heat maps, especially post-beanball, quite volatile. So, while Heyward's Whiff/Swing% has climbed as a rate on pitches off the plate and in thrown by lefties, it's worth noting that one whiff less would leave us in line with his prior numbers: Two whiffs out of 14 middle-in and off the plate equals a Whiff/Swing% of 14.28; one out of eight, 12.5%. There's nothing here to cause alarm. Due to the same reasoning, the drop in whiffs on inside pitches over the plate thrown by lefties isn't cause for celebration.

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Statistically speaking, the same conclusion presents itself as with the analysis of Heyward's overall performance: Heyward has not shown any indication that he cannot handle inside pitches from lefties any worse (or better) since Niese beaned him.