If you check out the major-league batting splits for 2009 to date, you can find the batting splits based on leverage.

For a brief description of leverage, you can check out the glossary here. Basically, each plate appearance can be assigned an index that indicates how big of an influence it has on the outcome of the game.

I've reduced the table to some stats of interest:

First, you can see that medium-leverage and low-leverage plate appearances have about the same frequency, whereas high-leverage plate appearances are about half as frequent. This tells you that in an average game, only about 1 out of every 7 plate appearances can have a large impact on the game's outcome. Interesting, huh? (That's not to suggest that runs scored during low- or medium-leverage situations don't matter--they just have less average effect on the outcome. Many of these are, for example, solo homers late in a game where the run differential is already 5.)

Calculating RBI per plate appearance, high-leverage situations come in at 0.22, medium at 0.10, and low at 0.08.

These numbers might be confusing. Some people interpret them to mean that players focus more during high-impact situations and drive in more runs. (Another way to refer to this is "clutch hitting.") In reality, the reason there are more RBI in high-leverage situations is that there are more runners on base. In other words, a situation with 2 runners on base is more likely to be high-leverage, whereas a situation with empty bases is more likely to be low-leverage. A homer hit in each case results in more RBI in the high-leverage case.

This explanation is backed up by the HR numbers. Here are the HR hit per plate appearance in each situation. High: 0.025, Medium: 0.027, Low: 0.029. They are pretty similar. I would presume that HR (as well as batting average) are slightly lower in high-leverage situations because they often see an effective relief pitcher (such as a lefty specialist or a closer) come in to face the batter.

Anyway, I will be looking at the performance of some specific players in these situations. I just wanted to introduce the numbers for starters.

This entry was posted on Tuesday, September 8th, 2009 at 11:53 am and is filed under Splits. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.