This blog’s purpose isn’t sabermetric in purpose (well, not entirely), but that doesn’t mean we won’t shy away from mentioning things like leverage and win probability when needed.
Here’s what you need to know.
The basic theory, is that given situation x–a score, an inning, a certain number of outs recorded, a certain number of runners on base, and even the baseball park in which the game is played, there is a certain probability that your team will win or lose the game.
As the game progresses, the win probability situation changes.
Those situations that are most likely to significantly alter the probability of one team winning or losing the game are known as high leverage situations. These are the late innings, bases loaded, one run games type situations.
Some really, really smart people have gone through and calculated a number to signify the leverage index for each and every potential situation. We’re, um, just gonna tell you to go visit The Hardball Times or Fangraphs if you want more information.
Thus, now if we show you a WPA graph, such as this one (and
we’ll probably be using these graphs from, Fangraphs, from time to time.)
You now know how to read it–the line is probability, the bars are the importance of the situation.