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Double plays by batting side: Is there a difference?

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Is there a difference in hitting outside pitches into double plays by side of the plate? You might be surprised at the results.

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Denny Medley-USA TODAY Sports

There are times the smallest thing sparks a post. I was reading the New Bill James Historical Baseball Abstract and noted this sentence in the discussion on former Phillie catcher Darren Daulton (p306):

A lot of double plays come when a hitter reaches for an outside pitch that he ought to take, and hits a ground ball to shortstop or second base.

There's nothing too startling in this statement — it's difficult to pull an outside pitch, and reaching across the plate to hit a pitch can often result in a weakly hit ground ball, not the desired result with runners on base.

With PITCHf/x data, we can empirically test this notion and see if it holds up. I use both Brooks Baseball and Daren Willman's baseballsavant.com frequently, but Daren's site allows for the download of data in an easier and more complete manner. I grabbed all the pitches in which a hitter grounded into a double play to see the pitch location. This is how Daren breaks down the pitching zone:

Savant Pitch Zones

This is from the catcher's perspective, so for a left-handed hitter, the balls described by Bill James would be Zones 11 and 13, and I also included Zones 1, 4 and 7. For right-handed hitters, it would be the opposite, Zones 12 and 14 as well as 3, 6 and 9. I checked with Daren to be sure, and in all cases, switch-hitters are listed by the side of the plate they were batting from in a given at-bat.

As I gathered enough for a first look, this emerged for left-handed hitters in 2014:

Year LHDP Outside Pct
2014 1275 802 62.9%

Excellent: There were 1,275 double plays hit by left-handed hitters, of which 802 were hit on pitches on the outside part of the plate or out of the strike zone, almost two-thirds. I don't argue with Bill James — he loses more baseball information in his morning shave than I'll ever acquire — but it's still fun to test notions and see what the data shows.

Then I gathered the data for right-handed hitters:

Year LHDP Outside Pct RHDP Outside Pct
2014 1275 802 62.9% 2331 917 39.3%

I've lost count of the number of PhD and PhD candidates who write for Beyond the Box Score (four?), but a significant part of any doctorate program curriculum is a solid foundation in advanced statistical analysis. I'll leave it to them to elaborate if they wish, but I suspect there's a big difference between forty and sixty-three percent.

I decided to go back to 2010 to see if this pattern held up:

Year LHDP Outside Pct RHDP Outside Pct
2014 1275 802 62.9% 2331 917 39.3%
2013 1344 857 63.8% 2388 870 36.4%
2012 1323 861 65.1% 2240 903 40.3%
2011 1297 844 65.1% 2229 854 38.3%
2010 1288 844 65.5% 2428 993 40.9%

Any time I see something like this, the very first thing that pops into my mind is error on my part. Daren has an option to show heat maps for given situations, and this picture shows it for three teams with a fair number of double plays hit by left-handed hitters:

Heat Maps

Data is from 2014; left-handed hitters are on the left, right-handed on the right. The left-handed batters really did hit the majority of their double plays on pitches on the far side of the plate, and it's far less pronounced for right-handed hitters.

I don't claim to be a baseball strategy expert, just a guy who likes to play with data and look for trends. It very well could be this is a sample size issue, since there are about twice as many plate appearances by right-handed hitters than left-handed, and what is seen in a smaller sample size might disappear in a larger one. I also checked to see if hitters were pitched more on the outside and saw no pronounced difference: Around twenty-six percent of pitches were on the far side of the plate for lefties, twenty-seven percent for righties.

I looked at several other possibilities: position the hitter played, distance the ball was hit, type of double play (i.e, 6-4-3, 4-6-3, etc.), position that initiated it, and the difference persisted. It is possible it's simply easier to turn a double play hit to the left side of the infield than the right, but that's a very unsatisfying answer, one step removed from "just because." Maybe the better defenders in general are on the left side, and I suspect there's something to that —generally, the shortstop is the best-fielding infielder and can make more plays than a second baseman, and certainly a first baseman.

There are numerous factors that go into double plays, such as game situation, pitcher, hitter, running speed of the hitter, where the defense is positioned, and the way the hitter is pitched. When there is such a wide disparity between sides of the plate and it's persistent, it's hard to let it go. It is common for pitches on the far side of the plate to be hit into double plays — for left-handed hitters. For right-handed hitters, not so much.

All data from baseballsavant.com. Any mistakes in amalgating and processing it are the author's. Be sure to drop a tweet to Daren and tell him how much you admire what he's done in making PITCHf/x and other data available.

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