Hitting pitches outside the strike zone: A visual analysis

My last post discussed how often batters swing at pitches outside the strike zone, with the general conclusion being it happens too often. I intended to expand on that notion in this post with a full-blown monstrosity of a Tableau data viz, but I don't have it in me to spring that abomination upon an unsuspecting readership. On the plus side, I can now confidently state that if one is interested in knowing if a database containing over 700,000 lines and 60 columns can be uploaded, the answer is yes . . . if you're patient. Very patient.

I still might drop that one in a future post, but in the midst of working with it I noticed a page I was about to delete because I thought it wasn't telling a very compelling story. Upon further review, I saw that with some refinement it graphically depicts the difference between swinging at pitches in the strike zone versus those that are outside.

This analysis looks at batting average and slugging percent for pitches that are put in play. This is not a new concept — for example, this Brooks Baseball page shows Javier Baez's batting average depending on pitch zone, and different tabs show slugging percent, isolated power and other values. This page from baseballsavant.com shows the batting average on pitches outside the strike zone for players with at least 200 at-bats and introduces an element of comparison to see how well players do compared to each other.

One last piece of introductory information — this chart, adapted from data at baseballsavant.com, shows the location of every pitch in 2014 depending on handedness of the pitcher and hitter:

All views from catcher's perspective

As expected, pitchers try to keep pitches in the heart of the strike zone to a minimum. Batters are already in a bind —pitchers have no interest in giving them anything to hit, making it incumbent on the hitter to be creative and make the best of what he's given.

How much better or worse are hitters when swinging at pitches outside the strike zone? This is shown in this screen grab of a Tableau data viz (view the actual viz here):

I'll use Javier Baez to explain. In 2014, he had a .283 batting average when the ball he hit was in the strike zone, but only .071 when the pitch was out of the strike zone. Over seventy percent of his strikeouts ended on pitches that were out of the strike zone. Since approximately half of his at-bats concluded on pitches out of the strike zone, there was a profound effect on his overall production and a primary reason why his final numbers were so disappointing.

Scrolling over the data points shows more information, and the data can be filtered by team. It's important to note that walks and strikeouts are tabulated using the location of the last pitch. Also, events in which there was no PITCHf/x data are not included, which is why the numbers won't match up precisely with official MLB stats. Viewing at-bats in this regard doesn't tell the entire story of a plate appearance, but it does demonstrate the difference in outcomes depending on where the pitch was, and thus proves that it's not a minor point.

Javier Baez is by no means alone in the dramatic difference in batting (or slugging, shown in the second tab), suggesting there's a very good reason why hitters are encouraged to not chase balls out of the strike zone and why pitchers routinely pitch there. The data viz only includes hitters with around 100 at-bats on pitches both in and out of the strike zone, and a difference of 100+ points in average and 300+ in slugging should be enough to get any manager's attention.

Numbers are only numbers until they're compared and contrasted with other numbers, and this shows what any casual viewer of Javier Baez saw last year: He was far too willing to swing at just about anything, sacrificing power when making contact with pitches that were off the plate and insuring it would be a rare plate appearance in which he'd see anything even close to a strike. However, this analysis uncovered a couple of players who managed to hit better on pitches outside the strike zone, the most intriguing being the Twins' Brian Dozier. He didn't hit for average in an equal opportunity fashion, but displayed power on pitches in and out of the strike zone, notable for doing it while playing in Minnesota and as a middle infielder.

There are no absolutes in baseball, but this trend is very clear — swinging on pitches outside the strike zone leads to lower average and reduced power. There are exceptions, but when the differences are this dramatic and stark, it behooves players to attempt to cut down on the pitches they swing at. If they're successful, it could force pitchers to work closer to the plate, which itself could reverse the decrease in runs seen over the past five years or so. If hitters are willing to swing at anything, why should pitchers throw strikes? That's the focus of my next post, when this data is viewed in terms of pitchers. Stay tuned.

All data from Baseball Savant. Any mistakes in gathering or processing the data are the author's.

Scott Lindholm lives in Davenport, IA. Follow him on Twitter @ScottLindholm.