Tuesday, December 13, 2022
Catcher Framing: Savant v Steamer
Here are all the catcher framing numbers for Savant and Steamer, since 2015, min 100 innings. The correlation is an extremely high r=0.92. In other words, they are both coming to very similar conclusions, even though their methodologies are independent of each other.
Is one better than the other? To the extent that I would choose a winner, I would choose Steamer. If we look at year to year correlations of Savant to itself, we get r=0.51. We also get the same correlation if we run a correlation of Steamer to next year's Savant. And we also get the same r=0.51 correlation with Savant to next year's Steamer. Where we get a slight win is Steamer to itself has an r=0.56.
Indeed, when we include both Savant and Steamer to forecast next year's Steamer, the correlation remains at r=0.56, showing that Savant is not including any new information. To that extent, I would argue that Savant is a subset of Steamer, or a Steamer-lite. If we correlate to next year's Savant, the correlation goes to r=0.52, which barely budges from the single metric correlation of 0.51.
These results, at least directionally, is as expected. Savant intentionally keeps the zones larger, while Steamer uses more precise plate location. Steamer might even create different shaped zones for bat-side, implicitly or explicitly including umpire effects. And for all these extra considerations, the gains are fairly modest.
Indeed, if you simply used called strike rate in the Shadow Zone, and did nothing else, the correlation would be just below .90 against Steamer. In other words, just doing the absolute minimum gets you most of the way there.
And so if you are trying to explain Catcher Framing to someone, and to try to convince them that the impact is real, simply quote the Called Strike Rate in The Shadow Zone. Jose Trevino for example led with a 54% called strike rate, against a league average of 47%. Getting an extra .07 strikes on the edge (meaning flipping a ball to a strike 7% of the time), on 2719 pitches, that comes out to an extra 190 strikes. That's a whipping 190 extra strikes. Divide by 8 to get that into runs. So, 190/8 is 24 runs. That's a simple back of envelope calculation. Doing a bit extra work that Savant does, and a better estimate is 17 runs prevented. Doing a bit more work that Steamer does, and they get Trevino with 19 runs. They are all in the same ballpark, however you try to figure it out.
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