"Robo-Umps" Would Upend the Careers of Many Pitchers and Catchers
If MLB does one day institute a full automated ball-strike (ABS) system, certain catchers and pitchers would be greatly de-valued.
While I may be an analytics guy, I do still value many traditional aspects of the game of baseball. The human element and subjectivity of umpire calls just adds something special; a bit of unpredictability that makes the game that much more exciting. Who doesn’t love watching a manager go ballistic on an ump when he blows a call? Yeah, your team may be on the wrong side of an ump’s gaffe at one point or another, but according to the law of averages, it all evens out in the end. One traditional aspect of the game I truly hope never changes is live humans calling balls and strikes. In recent years, the MLB has experimented with the “automated ball-strike system”, or “ABS” for short. Commonly referred to as “robo-umps”, the ABS system uses the Hawk-Eye tracking system to determine if a pitch is a ball or strike and sends the call to the home plate ump through an earpiece.1 Major League Baseball began experimenting with this system in 2022 in the Arizona Fall League and select Minor League ballparks. Beginning in 2023, Triple-A games started using full ABS, in which all pitches are called by the system for the first three games of each series. For the last three games of each series, a “challenge” system is used in which a home plate umpire calls balls and strikes and teams can challenge calls using ABS. Earlier this month, Major League Baseball pulled the plug on the full-ABS system for the time being and instead instituted the challenge system for all Triple-A games. Commissioner Rob Manfred cited surveys of both players and fans, which showed a clear preference of the challenge system over full ABS, as a key factor in this decision. This move puts the brakes on what once appeared an inevitable future of MLB balls and strikes being called by a computer. While this decision clearly appeals to the general consensus of players and fans, many of those players closest to ball and strike calls, the pitchers and catchers, are breathing a huge sigh of relief at the change of heart by baseball.
The Catchers
There are three unique facets of catching defense which, when combined, account for much of what makes a catcher valuable on the field. These are the ability to throw out baserunners, the ability to block wild/errant pitches, and the ability to frame close pitches to be strikes. Statcast measures these three values via their “Throwing”, “Blocking”, and “Framing” metrics. These metrics measure how many runs catchers save above the league average in each of these skills. Per Statcast, “framing is the art of a catcher receiving a pitch in a way that makes it more likely for an umpire to call it a strike”.2 It’s “Catcher Framing Runs” converts strikes to runs saved on a basis of .125 run-to-strike basis while adjusting for the pitcher and ballpark. The table below shows catchers’ stats and how they have ranked in these metrics in 2024, and gives a total defensive score to each by taking the geometric mean of the three rankings3
Now, the following table excludes framing from the calculation. It also shows the change in ranking for each catcher when framing is excluded from the defensive score.
Both Jose Trevino of the Yankees and Yasmani Grandal of the Pirates see their overall defensive rank drop 22 places. Patrick Bailey, identified as the top defensive catcher in the first table, drops out of the top-10 when framing is not considered. It is clear that if a full ABS system were to one day be implemented in baseball, the way we value catcher defense would drastically change.
The Pitchers
The “Shadow Zone” is the area that straddles the strike zone on all sides. Pitches here are basically called balls 50% of the time and strikes 50% of the time.4 Many pitchers attack this region and are skilled at getting batters to swing and miss, make weak contact, or take called strikes. The impact of the ABS system here would be on pitchers who thrive off getting fringe strike calls by making pitches just off the plate appear as strikes to umpires. If these pitchers lose the ability to exploit the human element, they lose a significant strength of their game. Statcast measures runs saved by pitchers when their pitches in this region are not swung at (called “take”). Certain pitchers to a better job than others at saving runs for their team by getting batters to take called strikes in this region. Below is a table showing the best pitchers by “take runs saved” in the shadow region relative to the league average.
If the MLB were to go to a full ABS system, pitchers skilled at fooling umpires would lose this advantage. Additionally, batters would have a clearer understanding of the strike zone given that the variability from umpire to umpire would disappear and the strike zone would become more standardized.
In Conclusion
An automated ball-strike system would surely alter the game of baseball, but would do so disproportionately for pitchers and catchers. Many catchers and pitchers would need to drastically alter their approach to the game and strengthen their skills in other aspects of their position in order to remain successful (or rostered, for that matter). While Major League Baseball should strive to ensure calls are as accurate as possible, removing the human element from this part of the game would alter catching and pitching, and negate the truly valuable skills of pitch framing and deception. It’s good that MLB decided to pull back on this initiative. Who knows, maybe with the retirement of Angel Hernandez, MLB will realize that the vast majority of umpires are in fact competent enough to call balls and strike themselves.
The Automated Strike Zone Is Slightly Different At Triple-A in 2023 (baseballamerica.com)
Statcast Catcher Framing Leaderboard | baseballsavant.com (mlb.com)
The geometric mean was used to neutralize the average being skewed by a catcher being extremely high or low relative to their rankings in the other two metrics.
Tangotiger Blog