Evaluating catcher defense has long been one of the banes of saberists everywhere. While there have been some strides in evaluating defense for position players — see: UZR, DRS – catchers are a separate world in and of themselves. There are a number of different defensive skills that catchers need to possess, and each of them has the potential ability to impact their overall value defensive: arm strength and accuracy, pitch blocking ability, pitch framing ability, and pitch selection.
At the moment, saberists have focused their research on the first three factors, as pitch selection is a tricky thing to isolate and does not reside solely in a catcher’s purview. You can currently find two the first two factors on FanGraphs: arm strength and accuracy, and pitch blocking ability.
rSB: Calculated by The Fielding Bible, Stolen Base Runs Saved measures how many “runs” a catcher contributes to their team by throwing out runners and preventing runners from attempting steals in the first place.
RPP: First calculated by Bojan Koprivica, Passed Pitch Runs (RPP) calculates the number of runs above / below average a catcher is at blocking pitches.
Both of these values are then added together, and account for the “Fielding” component in WAR for catchers.
Context:
Like all defensive stats, both rSB and RPP are centered around 0, meaning that a score of zero is considered league average. Scores above zero are good, and those below zero are bad.
| Rating | rSB, RPP |
|---|---|
| Excellent | +5 |
| Great | +3 |
| Above Average | +1 |
| Average | 0 |
| Below Average | -1 |
| Poor | -3 |
| Awful | -5 |
Note: these values are for each stat separately. If you would like tiers for catcher defensive value in total, double the values of the above tiers in order to get a quick-and-dirty estimate.
Things to Remember:
● While FanGraphs does not yet account for pitch framing, Mike Fast has made some remarkable strides measuring a catcher’s pitch framing ability. If you’re interested, be sure to check out his research.
● Next to RPP, you will also see the stat Calculated Passed Pitches (CPP). This is another statistic derived from Bojan’s research, and it measures how many passed balls a catcher should have allowed based on his pitches seen.
Links for Further Reading:
Catcher Pitch Blocking & WAR Update – FanGraphs
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