Batted balls and cheese

Stringers are in every major league park, and most levels of minor league ball, too. They manually record various aspects of the game as it progresses. If you’re watching an MLB.com Gameday feed, you’re seeing a combination of PITCHf/x data (speed, location, pitch type, etc.) and stringer observation (where the ball went, how it got there, who fielded it, etc.). There’s a level of detail that’s not often discussed—or present—in the Gameday information, that could provide assistance in evaluating pitches, and the pitchers who throw them.

Two weeks ago, I looked at the variation, or bias, shown by stringers when classifying batted balls. I take interest in such things since I’d like to calculate pitch-by-pitch run values based on the type of batted ball, not the outcome. In other words, I’m interested in line drives and fly balls, not outs and hits directly. While Gameday consistently provides classifications for line drives, fly balls, pop-ups and grounders, it often provides an nice little descriptor—soft or sharp. If you look closely, you’ll find that it is possible, according to some stringers, to bunt the ball sharply, or even hit a sharp pop-up.

Refresher on batted balls

Since clicking the link to an old article (two full weeks!) is taxing, here’s a breakdown of batted ball types and value and likelihood of various outcomes. (Outcomes being hits and outs, values being Linear Weights.)

Contact types

Now let’s layer on the cheddar cheese. Soft or sharp, or none of the above. Home runs are never sharp nor soft, and any play that has an error results from a normal batted ball. Allegedly. I give home runs their own contact tag, errors (and bunts) I’m usually ignoring.

Not every park (i.e., stringer) tags batted balls at the same frequency. The deeper we go, the more we need HITf/x.

AT&T is smack on the average (.0524). The difference between Busch III and Chavez Ravine is six-fold. That’s a problem, but I’ll forge ahead.

What’s a sharp liner worth to ya?

Breaking down the batted balls by contact type (and ignoring home runs), here are the event probabilities by batted ball type.

Line drives are the most likely to be tagged—nearly 12 percent. The sharp line drive yields more outs than the other types. It also gets fewer singles and more extra base hits. The soft line drive is turned into fewer outs, more singles and far fewer extra base hits. Intuitively, beyond the sharp liners being turned into more outs. I can speculate about the human factors involved, but I’ll leave that for the comments.

I suppose the soft pops are the bloops over the infield. Less than 2 percent of pop-ups are tagged, so not much to see here.

More than 9 percent of grounders are tagged. Not surprisingly, the sharp grounders have good outcomes—so good, they’re the best of the lot. Home runs not included, of course. A soft grounder is a good thing, too. This is the only type of the four that has more sharps than softs.

Fly balls are tagged as often as grounders, but lean heavily toward soft over sharp when tagged. Ground balls are tagged more on the sharp side, but the majority isn’t overwhelming. Sharp fly balls are, essentially, extra base hits. Soft fly ball outcomes are very similar to the same contact outcomes for both line drives and ground balls. I wonder if a soft fly ball and a soft line drive are actually the same thing.

Conclusion

We really need HITf/x. Well, we do have some data: 15,000 batted balls from April. Next week I’ll wrap up this series by comparing HITf/x data to various stringer tags—batted ball type and contact.

References & Resources
Batted ball classifications from MLBAM’s Gameday, data from 2009 MLB regular season through Sept. 13