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Tuesday, May 25, 2010
BIS: Taking BABIP one step further

By Ben Jedlovec, Baseball Info Solutions

You've probably seen stories on other websites citing Livan Hernandez as one of the luckiest pitchers in baseball in 2010, and Cole Hamels one of the unluckiest.

A look at their BABIP (Batting Average on Balls in Play) would tell you that they've probably been helped (Hernandez), and hurt (Hamels) by their defense this season. But looking solely at BABIP doesn't tell us that for sure.

But now our group has found a way to offer more concrete proof of how much a pitcher is being helped/hurt by his defense.

Here's how:

In our book, The Fielding Bible – Volume II we spent a lot of time trying to separate defense from the legendary “pitching and defense” that wins ball games. We took individual defensive performances and broke them down to provide accurate defensive assessments.

What I soon realized was that by isolating defensive performance we also managed to come up with the roots of a system to evaluate pitchers independent of their defensive environment.

Sometimes the defense makes a nice play and helps out the pitcher. Other times, it falls between two miscommunicating fielders for a hit.

Often, the fielder is standing in just the right spot at the right time. None of this is under the pitcher’s control, but he gets credit for it regardless of the outcome.

If life were fair, these anomalies would even out over the course of a season.

Based on the characteristics of each ball in play (location, trajectory, etc.), I calculated the approximate chance that the average defense converted the ball in play to an out.

I added up this probability for every ball in play over each game and over the full 2010 season to arrive at an expected number of hits allowed given the distribution of balls in play.

Without boring you with the details and adjustments I made (for now), I’ll present a list of the “luckiest” and “unluckiest” pitchers this season (please note that our BABIP calculation may differ from others due to differing treatment of bunts)

The 3 Luckiest
1- Livan Hernandez
Hits Allowed: 40
Expected Hits: 55

Conclusion: Hernandez has allowed 15 fewer hits than expected. Had he allowed 15 more hits, his BABIP would have risen from .183 to .267

2- Doug Fister

Hits Allowed: 40
Expected Hits: 52

Conclusion: Had Fister yielded 12 more hits, his BABIP would jump from .225 to .294

3- David Price
Hits Allowed: 45
Expected Hits: 55

Conclusion: Had Price allowed 10 more hits, his BABIP would rise from .241 to .300.

Hernandez, he of the 19 strikeouts against 18 walks in 55 innings pitched, rates as the most fortunate pitcher in baseball. Based on the locations and trajectories of Livan’s balls in play, we’d expect 15 extra hits to have fallen in. But instead, those plays became outs.

One rule of thumb is to expect every pitcher’s Batting Average on Balls In Play (BABIP) should move toward the league average (around .300) as the season progresses.

In each of the three cases, we find their Expected BABIP to be closer to the league average than their current BABIP.

The 3 Unuckiest

1- Brad Bergesen
Hits Allowed: 60
Expected Hits: 48

Conclusion: The Orioles have played poor defense behind Bergesen. An average defense would have turned 12 more outs on the balls he allowed into play, cutting his BABIP from .327 to .251.

2- Doug Davis
Hits allowed: 48
Expected Hits: 39

Conclusion: Had the Diamondbacks performance behind Davis matched that of an average defense, his BABIP would drop from .400 to a more reasonable .320.

3- Cole Hamels

Hits Allowed: 60
Expected Hits: 51

Conclusion: Hamels is bound to catch a break at some point. His BABIP of .316 would be 55 points lower if the normally-good Phillies defense had performed well for him.

In theory, utilizing hit locations and trajectories will lead us to better pitching evaluations. The next step is to refine the technique and evaluate its predictive power on historical data, and hopefully we'll get the chance to follow that up with further study in the future.