Tuesday, June 30, 2020
RE24: Of Found and Lost Runners
When working with things like Run Differential or Pythag records, baseball presents a unique problem: a game can end with run potential still on the bases. Imagine for example, it's a tie game, the bases are loaded with 0 outs. This has a run potential of 2.3 runs. But not in the bottom of the 9th inning. Indeed, if you get a walk with bases loaded and this is the first 8 innings, you get a run, and the run potential is still 2.3 runs. But in the bottom of the 9th or later, you get a run, and those 2.3 runs... well, they are still there. It's not 0. Otherwise, you would go from 2.3 to 1.0 and you would lose 1.3 runs.
Maybe I said that too fast. Before the 9th inning, the starting run expectancy with bases loaded and 0 outs is 2.3 runs. You get a walk and bases are still loaded. So, the ending run expectancy is 2.3 + 1 run for the actual run. So, that's 3.3 runs after the event, and 2.3 runs before the event. That difference is 1.00 which we ascribe to the bases loaded walk.
But in the bottom half of the 9th, it either ends at 2.3 + 1, or it ends at 1. And since the starting RE is 2.3, then you either gained 1 run, or lost 1.3. There is, in effect, 2.3 runs that are on the bases that are simply...lost. But, if you wanted to do something like Run Differential for team evaluation or Pythag purposes, you WANT those 2.3 runs on the board. You need them.
Why do I bring this up? Because this year, in extra innings, we will find 0.6 runs at the start of each of those innings. That's because the run expectancy will increase by 0.6 runs by simply placing runners on base. Since both teams are getting the same benefit, this will cancel out. But, you have to be careful how you handle this. Those 0.6 runs, while officially belonging to the pitcher starting the inning, analytically belong to no pitcher. It's like the inherited runner of a reliever. Except there's no handoff from another pitcher.
So, the RE24 approach works, whether with Found or Lost Runners. And so, when doing work with Runs or Run Differential, relying on RE24 instead of actual runs will get you to where you want to be.
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