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Pitching success and the strike zone: Another visual analysis

How does pitcher success change on pitches inside or outside of the strike zone? This post shows it visually using batting average and slugging percentage.

It would be far better for CC Sabathia if the pitch is outside the strike zone.
It would be far better for CC Sabathia if the pitch is outside the strike zone.
Benny Sieu-USA TODAY Sports

My last post showed the distinctions when hitters swung at pitches inside and outside of the strike zone using PITCHf/x data gathered from Daren Willman's Baseball Savant to show differences in batting average and slugging percent. In general, hitters batted 100 points or lower and slugged 300 points or lower when making contact on pitches outside the strike zone, which makes perfect sense -- it's hard to drive a ball that isn't down the heart of the strike zone.

This data can be used to see contrast for pitchers as well, although the conclusion isn't as cut-and-dried as it is for hitters. In 2014, approximately sixty percent of pitches were outside the strike zone, possibly due to the combination of both pitchers working outside the strike zone and hitters willing to swing at those pitches. This creates a different dynamic for pitchers in that if they throw a mistake down the middle of the plate with no movement, hitters will pounce and attempt to take advantage of what might be the only hittable pitch in a given at-bat. In other words, hitters may be waiting for one pitch they can do something with, whereas pitchers are mixing up pitches and trying to keep hitters off-balance. Sometimes those pitches won't do exactly what the pitcher had in mind.

This Tableau data viz shows both batting average and slugging percentage on the final pitch of an at-bat:

It's the same data viz referenced in my previous post, but with any luck it will actually be embedded in the post this time (long story -- don't ask). The pertinent tabs for this post are Pitcher BA and Pitcher SLG, and I'll use CC Sabathia to explain what the data shows for pitchers.

Against Sabathia in 2014, hitters batted .405 when the pitches they put in play were in the strike zone and .159 when the pitch was out of the strike zone, a difference of 246 points and one of the highest differences in the league last year. I added one other element that is not included in the batting pages, the total number of pitches. This table shows the percentage of pitches hitters put into play depending on whether they were in or out of the zone:

Pit AB Pct
In Zone 325 111 34.2%
Out of Zone 473 82 17.3%

Hitters are attempting to take advantage of those few pitches in the heart of the strike zone they may be able to do something with, but there will be pitches such as 95 mph fastballs that hitters swing and miss at (not in Sabathia's case, however -- he topped out at 92.2 last year).

As I stated in my last post, this data isn't the final word on the use of the strike zone for either pitchers or hitters, particularly in the case of the pitcher since there's a very good chance the hitter attempted to take advantage of a hittable pitch. But it does illustrate why pitchers are loathe to pitch in the strike zone -- and why hitters should be more patient and force them to stop pitching outside.

I don't claim to be one of the great baseball minds, uncovering new trends and insights through the creative use and application of advanced data. I use data to expand, illuminate, augment, and explain common sense in baseball (and other areas of life). PITCHf/x data helps explain how often pitchers are in or out of the strike zone and the ramifications of pitches in a given area. Baseball has known these differences for years, even before PITCHf/x, but it's still an increase in knowledge to see how often a given event occurs. It helps explain the differences between the 4-A pitchers and hitters and solid major leaguers -- in the case of hitters, it's the ability to lay off the outside pitches, and for pitchers the ability to paint the corners without giving hitters something they can drive.

My basic point remains the same as in my prior post -- hitters are ill-served by swinging at pitches outside the strike zone, and pitchers will have more success in pitching outside the zone. There is nothing momentous in this statement, but it's still fun to see the data illustrate it.

Data adapted from Any mistakes in gathering and processing the data are the author's.

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