Stats Sunday – BABIP

The following post was part of 2012′s Stats Sunday series. Thanks to Len Kasper for writing it.

For this week’s Stats Sunday feature, we focus in on Batting Average on Balls In Play or “BABIP.”  Pretty simple concept–you essentially take out a player’s strikeouts and homeruns and figure out what his average is on everything hit in the field of play.  The league-wide average is usually right around .300.

Because this particular stat tends to fluctuate a lot and show randomness from year to year, the prevailing thought is that it’s something “generally” out of a player’s control.  Stats that show consistency (either good, bad or average) tend to carry more weight as controllable skills because a pattern develops.

Also, the prevailing thought is that in general, pitchers don’t have a lot of control over balls in play (they do in terms of homeruns, strikeouts and walks, but not balls that require their defense behind him to handle).  Please check out Voros McCracken’s stellar work for more on Defense Independent Pitching Stats: http://vorosmccracken.com/.

I like BABIP because it is an interesting stat for BOTH batters and pitchers.

Here is the bottom line:  if a batter’s BABIP is well about .300, chances are he will regress back to near that average at some point (or, in some cases, simply back to his career BABIP) because he may be getting a little lucky on balls in play.  If he’s well under .300, he may be a little unlucky.  For pitchers, it’s the opposite:  a .375 opponents BABIP means he might be unlucky while a .246 opp BABIP may say he’s getting lucky.

So, for instance, if a batter is putting up huge numbers in June and his BABP is .410, but his career BABIP is .330, at some point, the meter might run out and he may see a return to earth.  Conversely, if a pitcher through 12 starts has a 5.10 ERA but a BABIP of .386, he might be due for some good luck on those balls in play at some point.

There are other variables which can affect BABIP, like a batters speed, a pitcher’s groundball rate, the quality of a pitcher’s defense behind him.

But again, it’s a good tool just to help put into context for us what kind of season a player is having and whether we should be encouraged, discouraged or feel that his numbers are just about right where they should be.

Here are a couple of excellent articles about BABIP, which explain the stat much better than I and give you some things to think about:

Fangraphs

http://www.fangraphs.com/library/index.php/offense/babip/

Yahoo Sports

http://sports.yahoo.com/mlb/blog/big_league_stew/post/Everything-you-always-wanted-to-know-about-BABI?urn=mlb,203710

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