Swinging at Strikes

For every pitch, a batter has to make two decisions:

1. Is the pitch a strike?
2. Should I swing at the pitch?

(If the hitter has two strikes on them, it simplifies the equation).

Yet pitchers want hitters to swing at balls outside the strike zone and not swing at balls inside the strike zone. Taken together, the relationship between the pitcher and batter is a little bit like a shell game.

I feel like I’m writing a lot about the Reds starting pitching, so we will use the bullpen to look at pitcher swing percentages.

Here is the first interesting aspect of the pitcher-hitter relationship: hitters will swing at about 46% of all pitches thrown (league-wide stat, 2014). Here is how our bullpen compares to the league wide swing rate:

With the exception of Same LeCure and Partch, our bullpen is all hanging around the 46% mark.

Yet some pitchers can get hitters to offer at balls outside the strike zone or make hitters whiff at balls thrown inside the zone. Here is a breakdown of how often our relievers can get hitters to offer at pitches outside the zone (called O-Swing%):

Predictably, these numbers are lower than the overall swing percentage. What is a little surprising is how low Sam LeCure’s number is here: since he is not able to get hitters to offer at pitches outside of the zone, it hints at a possible regression in his pitching line later in the year. His BABIP (.278 vs .297 career) also indicates there could be a bit of a regression as the season moves on.

Also not surprisingly, pitchers who have powerful breaking pitchers (Chapman, Marshall) have higher O-Swing% than the other pitchers on the list.

Next, here is how often hitters swing at pitches inside the strike zone:

From this list, it’s easy to see that Major League hitters can diagnose balls in the strike zone with amazing consistency. Ondrusek and Hoover, when they throw the ball over the dish, are not fooling anyone. Sam LeCure, on the other hand, seems to be able to confuse hitters when he wants to sneak a pitch over the plate.

So that tells if pitchers have the ability to get hitters to swing at pitches outside of the zone (or misjudge pitches inside the zone), but what happens when the hitter swings at these pitches? Here is the contact rate (hits, outs, or foul balls) for pitches thrown outside the strike zone (O-Contact%):

Yikes, Trevor Bell. Thankfully that’s an artifact of a small sample size. Some of our pitchers are very effective at inducing a whiff when hitters offer outside the zone (Chapman, Parra) while others are going to end up with some sort of contact (Christiani, Hoover). This is not always bad because contact outside the zone is much less likely to result in a hit than an out.

What about for balls inside the zone (Z-Contact%)?

In the back of your mind, you might have had the feeling that pitchers need to go outside the strike zone in order get a hitter out. Major league hitters, on average, are extremely good at making contact with pitches that are thrown over the plate, but the contest shifts dramatically in favor of the pitcher if the pitch is thrown outside of the zone.One of these things is not like the other things. But we already knew that.

From this list you can see how incredibly hard it is to get a hitter to swing and miss on pitches inside the strike zone. Remember this chart next time you hear someone say that pitchers need to “pound the strike zone.”