This is the second post in a series that I began awhile back in an attempt to break down the advanced concepts developed by the saber metrics movement, into more concise and relatable terms. If you missed it the first post can be found here, it covers the idea of stockpiling value as opposed to talent. In this post I’ll tackle the rapidly evolving view of how a catcher can impact the game on defense, and how the Marlins very own J.T Realmuto stacks up.
Now the most traditional way to evaluate a catcher’s performance is how effectively they control the running game. Stats like caught stealing percentage have been quoted for a very long time as the main way to evaluate talent behind the plate. It certainty bears relevance, part of the catcher’s job is to make a fast and accurate throw in order prevent a stolen base, but judging based on this result has it’s problems.
Namely that other factors like the pitcher’s ability to hold the runner/deliver the ball to the plate quickly, and the base runner’s speed/quality of jump ca-n muddy the picture. In this case an old scouting meter is probably much more effective, it’s called pop time and measures the time between the moment the ball hits the catcher’s glove, to when it hits the SS/2B’s. It’s a great tracker, and tough to fool since it covers receiving, ability to get out of the crouch, and arm strength. For a rule 2.0 seconds is Major League average, anything under 1.80 is elite.
The Great news for Fish Fans, J.T. Realmuto rated among the best in the league last year in this. Not surprising given his athleticism and background as a run & gun quarterback.
Now we get to the two more modern aspects of Catcher defense, blocking and pitch framing.
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I’ll start with blocking. This doesn’t refer to blocking the plate, that’s not a thing anymore, instead it means the catchers ability to get in the way of wild pitches and prevent runner’s from advancing. Traditionally there is a distinction made between a wild pitch and a passed ball, that distinction is important for understanding the issue, you don’t want a catcher up there constantly dropping the ball, nor a pitcher spraying WP all over the back stop, but when it comes to the Catcher’s ability to control damage they are effectively the same thing.
These traits are measured by a statistic called RPP or Runs on Passed Pitches, it’s a very heavy mathematical formula that’s used to calculate the stat, if you want to read about it here’s the creators explanation, but essentially the difficulty of the block is rated based upon velocity and distance from the catcher’s starting position. Catchers are then rated based upon both how often they make the block, and the difficulty of the blocks they make.
Now there’s an obvious flaw in this methodology, some backstops catch pitchers that never throw WP, thus don’t get a chance to showcase their ability to prevent runners from advancing. But it’s the best way we have of measuring, and when run against the eye test the players you would expect to score highly do.
Checking in on J.T he doesn’t score quite as highly here, RPP rates him as being a -0.1, just barely above average. It’s an extremely small sample size, and RPP takes a very long time to normalize, so don’t worry too much about the early returns.
Finally we have arrived at the much talked about pitch framing, or as catchers themselves call it, presentation. The theory, which is supported by a great deal of evidence, is that the way in which a catcher receives a pitch can have a dramatic affect on whether it is called a strike or a ball, particularly near the bottom of the strike zone. Catchers that keep a solid arm and avoid sudden movements while catching the ball clean have been able to steal a significant number of called strikes that should have been balls, while those who fail to do these things can cause the strike zone to shrink.
With the advent of pitch f/x presentation has become the easiest aspect of catcher d to track. We know exactly how often pitches thrown to a catcher outside the strike zone are called for strikes, and visa versa. Obviously some of this is umpire impacted, which is why a substantial sample size should be collected before drawing iron clad conclusions.
That being said this is a Marlins site, so I’ll excuse the small sample size problem and take a little look at the early return on J.T’s framing skills. I can tell you right off the bat they aren’t pretty, Baseball Prospectus rats his framing as being worth -15.9 runs in 2015, Statcorner (a separate site with a slightly different methodology) rates it at -14.9. As I said before it’s a small sample size, and his framing in the minors was above average so there is hope, but those numbers are bad and the minor league methodology is much less trustworthy so I wouldn’t hold my breath.
So there you have it, the three physical elements of catcher defense, In addition there is game calling/staff management, but that is difficult (near impossible) to quantify. Sorry for the length, hopefully you come away from this with a better understanding of how saber-metricians view catcher defense.