At Driveline, we implement player-development systems based around metrics that will ultimately optimize performance. For example, from a pitching standpoint we work on developing velocity, designing pitches, and maximizing recovery, among other systems. This intuitive, multi-faceted approach is already being applied in hitting, but we can further apply this to other positions on the field.
Let’s start with the other half of the battery, the guy behind the plate.
We could spend a long time breaking down the ways in which a catcher’s value is determined: receiving, hitting ability, pitch calling, arm strength, etc. But for now, let’s isolate it down to a job they are most well-known for and is also unique to their position: throwing out baserunners.
First, in order to create change and have an impact on a specific metric, we need to understand how it’s measured and broken down. In this case, pop time, or the amount of time it takes for the baseball to travel from the catcher’s glove to the fielder’s glove at second base. While we are aware that other components factor into a runner’s being caught stealing (pitcher’s time to the plate, accuracy of the throw, fielder’s tag, etc.), we also know that pop time is highly correlated with runner’s getting caught stealing.
Let’s break down pop time into two segments:
- Exchange time: the time from a catcher’s receiving the the ball to releasing it.
- Ball flight time: the time from a catcher’s release to a fielder’s receiving the ball.
“As a catcher and coach, when we say that we are going to work on throwing today…[this] turns into an exchange and footwork day instead…not often do we spend time developing arm strength.”—Jacob Garcia, graduate assistant at the University of Washington and former collegiate catcher at University of Northern Colorado
Currently in baseball, there is a persistence that exchange time is the primary determinant of improving a backstop’s value on limiting basepath advances.
Baseball twitter: what do you think is the most important aspect factoring into a catcher’s pop time?@Alex_Caravan and I are working on a little side project breaking down catcher statcast data at @drivelinebases
— Anthony Brady MS, CSCS (@BaseballFreak_9) October 6, 2018
As referenced above, the majority of practice time and skill work is spent on transfer technique aimed at decreasing exchange time. Intuitively, this makes sense. Getting the throw off quicker means that the ball should arrive to the fielder faster.
But why not look at the larger component of a base-stealing attempt: ball flight time? The actual throw from the backstop to second base covers approximately 127 feet (some quick Pythagorean math can derive this for the skeptics); it takes just over a second (1.0025 secs) for an 87-mph throw to travel from home plate to second base, and that is without accounting for the ball’s decelerating over time due to factors like drag.
Over a full second is comfortably higher than any major-league catcher’s average exchange time. (The lowest across all qualifying catchers in 2018 was 0.84.) And that’s with an 87-mph throw, which in 2018 was faster than most catchers’ top 10% of throws (faster than 33/46). To further put that into perspective, from 2015 to 2018, exchange time made up only 36.6% of pop time, with ball flight time making up the other 63.4%.
Note: For all analyses and numbers in this piece, we looked at only catchers who had at least 15 throw attempts to 2nd base in said individual year.
So if ball flight time is the largest contributing factor to pop time, shouldn’t there be a greater emphasis on reducing that factor, rather than primarily focusing on exchange time reduction? Furthermore, transferring the ball from glove to throwing hand and into release is a highly technical skill that happens in a short amount of time. Because of this, the exchange is arguably not only a hard skill to master but also even harder to teach and improve.
Alternatively, ball flight time can be reduced by simply throwing the ball harder. While that may not necessarily be easier, here at Driveline, we have a pretty good idea on how to develop arm strength and increase throwing velocity. Before we go any further, let’s dive a little deeper into the stats.
Conveniently, Statcast measures the exchange time the same way as it’s defined above, the time from a catcher’s receiving the ball to releasing it. While you can simply calculate ball flight time (pop time – exchange time), Statcast measures arm strength, which we can use as a predictor of ball flight time.
Note: Arm strength signifies the average of the top 10 percentile of all throws for said catcher since Statcast has not yet released throw-by-throw data.
Looking at these metrics for all qualifying catchers in the Statcast era (2015–2018), we can glean a few notable facts just from a quick surface-level analysis.
First, exchange time and arm strength are both significantly correlated with pop time for each year by ANOVA one-way results. Second, each year shows a stronger correlation between arm strength and pop time than between exchange time and pop time.
So yes, reducing exchange time (something catchers universally are trained in and work on) does help in reducing pop time. But more importantly, arm strength (something catchers are much less frequently trained in and focus on) seems to help even more in reducing pop time. (The difference in the strength of correlations was not significant, after a Fisher Z transformation.)
Below are the cold, hard (less glitzy) numbers on the strength of the R-squared values, the square of the correlations.
Arm Strength and Pop Time
But If I try throwing harder, won’t my exchange time slow down?
Analyzing the relationship between these catchers’ arm strength and exchange times, we see a near-nil correlation between the two. In other words, there’s no reason to fear that training will impact the ability to excel in the other one. In addition, looking at descriptive statistics for sub-segments of our population of pitchers, there is no discernable difference in average exchange times between the hardest and the softest throwers.
Graph: A measure of the average exchange times for the noted time periods with their standard errors being noted as tick marks.
A t-test comparison between any of the potential pairings fails to yield significant results; the highest t value only reaches an absolute value of around 0.5 units and a subsequent p-value of 0.33.
Implications and Applications
Based on the breakdown and stats outlined above, there is an argument that catchers should emphasize developing arm strength at a similar level so that exchange technique is emphasized. And that is strictly from the standpoint of throwing out baserunners. Prioritizing arm strength, recovery, arm health, and proper throwing mechanics is extremely valuable for catchers as they throw a baseball more times during a game than any other position. Because of this, there should also be more of an emphasis placed on recovery, arm health, and proper throwing mechanics.
NOT All Catchers Are the Same
Individualizing development is still king. There is not a one-size-fits-all model for catcher development—and there probably never will be. Understanding the breakdown of catcher pop time is valuable for coaches to target specific player’s weaknesses. A catcher with a cannon for an arm and poor exchange technique is in a spot where the majority of the focus should be on skill work aimed at reducing that exchange time. Alternatively, a catcher who comes into a program with elite transfer technique and an average-to-below average arm does not have very much room to improve and refine exchange time with further drill work. However, such a catcher may be in a great place to significantly improve pop time by prioritizing arm strength and implementing a program based around that.
Low-hanging fruit in sports analytics is becoming more and more scarce. Let’s take a moment to appreciate a fairly easy and simple revelation that taps into a baseball catcher’s ability to improve part of their game. While throwing hard might be the best determinant in throwing out runners on the basepath, throwing hard is not something that a catcher’s training program focuses on with appropriate weight.
This article was co-authored by Biomechanist Anthony Brady and Quantitative Analyst Alex Caravan.