One of the primary, if not the primary function, of a manger is to place the correct players in the correct situations for the good of the team. Bullpen usage, while maybe not the most important of the playing time decisions, is one that tends to stand out in fans’ minds. In an attempt to get our minds wrapped around which players are being put in the correct situations, who is being used in the toughest spots, and other similar questions we will turn to an investigation of leverage index.
Throughout most of the remainder of this article I will be referring to different leverage index bands. I’m defining those bands the same way that Baseball Reference does: high leverage is a leverage index greater than 1.5, medium leverage is a leverage index between 0.7 and 1.5, and low leverage is below 0.7.
The first, and simplest look at pitcher leverage index is to see which pitchers have entered the game with the highest percentage of high leverage situations. The following table was generated from data from 2006-2010. Pitchers needed to have made at least 150 appearances over the five-year span to be included in the list.
|Pitcher||High Lev %|
Despite the way managers handle most closers, using them only in the ninth inning when there is a save situation, this list remains populated with pitchers who are closers. This list in not meant to imply that these closers are being used optimally or even near optimally. There are plenty of times where these pitchers were used in low leverage situations, or there were higher leverage situations in the eighth inning that these guys would have been better suited to pitch in.
The list does say, though, that these pitchers have appeared in a higher percentage of high leverage situations than have their bullpen brethren. As a point of reference, a glut of top setup men over that time period— Scot Shields, Luke Gregerson, Matt Thornton)—are bunched at approximately 50 percent high leverage situations.
This list was built over an extended time period, so it includes many factors including true talent changes, role changes and team changes. With that in mind it might be insightful to look at some of the top single seasons over the same time frame. The following table summarizes the results.
|Pitcher||Season||High Lev %|
The table is again a list populated with all pitchers who were closers at the time. It appears that it is possible, depending on the season, to have pitchers appear in high leverage situations 70 to 80 percent of the time, with top setup men appearing on the list in the mid 60 percent range. We will talk about Mr. Aardsma and his appearance on this list twice in some depth a little later.
The previous two lists have looked at the top of the crop, but what does the bottom look like? Who are the pitchers who have been sent to the mound in the least stressful situations over the past five seasons? First from the perspective of lowest percentage of high leverage situations:
|Pitcher||High Lev %|
and then from the perspective of highest percentage of low leverage situations:
|Pitcher||Low Lev %|
As expected those lists are populated with journeymen relievers. These are the guys who are sucking up innings in blowouts, the infamous long relievers who are the 11th man on a pitching staff (12th or 13th if your manager happens to be Tony LaRussa). These pitchers, in any particular season, are pitching approximately 60 percent of the time in situations that are not vital to that particular game. That is not to say that these pitchers do not have roles, as some pitcher clearly has to pitch in those situations. It would be folly to pay these pitchers anything over the league minimum for the low impact service they are providing.
Young or old?
I thought would be interesting to investigate the relationship between age and leverage. As a Cardinals fan I have watched Tony LaRussa make young pitchers prove themselves before he will put them in a high leverage role. My going-in assumption was that this was probably a fairly common managerial tactic across the league. What do the data say?
The chart depicts on the aggregate how often players of each age are placed in high leverage situations. The generic trend in the data does seem to back up my assumption. Generally speaking, older pitchers are placed in a higher percentage of high leverage situations than younger pitchers. Clearly the trend is not overwhelming, and there are some sample size and selective sample issues on the periphery. Additionally, the talent level for each age needs to be considered and corrected for before any age bias in managers could be concluded with any level of certainty. All caveats aside, it does appear that LaRussa is not the only manager who slightly prefers veterans in high leverage situations.
A few anecdotes
David Aardsma has one of the more interesting reliever journeys, at least when it comes to leverage index, that I found while compiling the research for this article. In 2006 and 2008 he posted some of the lower single season totals for percentage of appearances in high leverage situations, 11 percent and 21 percent respectively. Then, after being traded to Seattle and installed as the closer and showing better peripherals, he promptly posted two of the highest single season totals as seen in the table near the beginning of the article.
One of the more dramatic changes in the other direction is Scot Shields. After posting seasons above 50 percent high leverage appearances from 2006-2008, Shields had injury trouble in 2009 which appears to have led to a higher walk rate and lower strikeout rates. Those lower peripherals, and the true talent level that produced them, led the Angels to use Shields in high leverage in only four of his 43 appearances.
Those are just a couple of examples of how usage can change over time because of changes in scenery, role or talent level. Clearly we could investigate the data and find other such examples. I thought those two were interesting because of how high they two ranked on the various lists.
This article merely scratched the surface on reliever usage. There are many more things that could be done with the data, correlating salary with leverage for example. That said, I found the fact that the top 10 high leverage percentage pitchers were all closers. I expected to find a few more setup men higher on the list. Also, while the age graph was not surprising, I did think it was interesting and worthy of additional investigation.
References & Resources
Leverage data from Baseball Reference.
Daniel Moroz at Beyond the Boxscore recently had an article on the subject of closers and leverage index.