The bullpen. It is probably the most volatile and unpredictable piece of a major league baseball team. Even for a team that was the World Series runner up and likely features the best closer in baseball, there are several question marks as we are about to enter Dodgers 2018 spring training.
We just gave you a look at the Dodgers 25-Man Roster, now let’s dive a little deeper and further examine the bullpen specifically. There are traditional stats that we use to evaluate pitchers like wins/losses, ERA, WHIP, and for relievers, saves of course. Sabermetrics has given us Field Independent Pitching (FIP), Batting Average on Balls In Play (BABIP), and Wins Above Replacement. These have become more commonplace in mainstream baseball circles the past few seasons. However, none of these tools provide the best metric to evaluate how relievers perform in high leverage situations; the save is not the end all. Many times, the closer comes into the ninth to shut down the opposition, while no one was on base and the team had a comfortable lead. How do we evaluate a relievers performance in a high leverage, pressure packed situation?
I don’t have the complete answer for you, but I offer a starting point. The Leverage Index. Otherwise known as LI, or pLI, or inLI, gmLI, or exLI! These offer descriptive snapshots of the leverage situation that the reliever entered the game under. Basically, the index takes into account the inning the reliever entered, how many runners were on base, and the score of the game at the time. Utilizing this index places that reliever’s stats in a clearer context, or at least this author thinks so. I will utilize the pLI, which is the Average Leverage Index. A pLI of 1 indicates the pitcher is average, while a pLI above 1 is above average, and a pLI below 1 is below average. If you would like to delve more into the various Leverage Index tools, go check out FanGraphs.
In order to set a baseline of understanding of LI/pLI, let’s start with the best closer in baseball, LA’s very own Kenley Jansen.