Next season, umpires will continue to make ball-strike calls. A challenge system will be added. Pitchers, catchers, and batters will be allowed to challenge ball-strike calls. Each review will take about 15 seconds. In each game, each team will be allowed to challenge until they accumulate two upheld calls.
In the last ten years, baseball has made many changes to improve the game.
“To start the 2014 season they had this new thing called instant replay. I can’t imagine the game without it today. I think we’ll say the same thing with all the rule changes and all the things they’re trying to do to make this game as clean and as natural as possible. With new technology and the things that can get it right, I think players are for it, for sure. As I am.” — Torey Lovullo
In 2023 and 2024, in the minor leagues an automated system for calling balls and strikes was experimented with. Possibly because of the need to make decisions about the strike zone, it was decided to proceed with only a challenge system.
“Triple-A ballparks used ABS this year for the second straight season, but there is little desire to call the strike zone as the cube defined in the rule book and MLB has experimented with modifications during minor league testing.” — Ronald Blum, November 2024
The Joint Competition Committee (JCC).
“Zac Gallen is on the Competition Committee (comprised of six owners, four players and one umpire) and heard first-hand on a call Tuesday morning that baseball is moving forward with another significant change.” — Alex Weiner
The JCC approved the Challenge System 9-2. Also, baseball teams approved the Challenge System 23-7.
“USA Today’s Bob Nightengale reported that 23 of 30 clubs voted in favor of the change, along with all six owners [in the competition committee]. Gallen said based on the results, the players submitted three yes votes and one no. The umpire voted against the measure.” — Alex Weiner
The Challenge System was used successfully in spring training.
“During Spring Training, a challenge system was used not unlike the one already utilized in the majors for instant replay on the bases. Each team started the game with two challenges available to them, and would retain their challenge after using it successfully or lose it after using it incorrectly. As noted by Ronald Blum of the Associated Press just before Opening Day, teams challenged 2.6% of called pitches during the spring with just over four challenges per game and a success rate of 52.2% overall. If those numbers were to hold, that would mean the ABS challenge system overturns just two ball-strike calls in the average regular season game.” — Nick Deeds, MLBTR
“I think the fans are gonna love it. I think it’s gonna add a new dimension to the game that fans really get into, just because there’s tension and excitement when someone challenges and you see it on the board.” — Tim Tawa
Several visualizations of the strike zone exist. Strike zones visualizations range from the zone in each umpire’s head, to the Umpire Scorecard Estimated Umpire Zone (EUZ) (it differs for each umpire and each game), to the broadcast zone (it has flaws), to the official zone. The Challenge System will include it’s own visualization. Although it may be closest to official zone, it was said that the challenge zone may differ slightly at each venue.
“What any individual thinks of as the strike zone is unlikely to be perfectly identical to the zone used in ABS, and that’s supported by the fact that nearly half of challenges made to umpire calls wound up being incorrect. That suggests players aren’t always more in tune with what the true strike zone looks like than umpires are, and a move to fully automated ball-strike calls could be a jarring adjustment for both pitchers and hitters as they adapt to a more accurate but wildly unfamiliar strike zone.” — Nick Deeds MLBTR
“I like it [The Challenge System] better than just a fully automated zone because it still allows for catcher’s framing to a certain degree. But the biggest issue for me right now is… there’s about four different strike zones that are being used to be judged.” — James McCann
“Consistency metrics provided by @UmpScorecards represent the proportion of taken pitches considered consistent with the umpire’s established zone in any given game. Our algorithm begins by finding the ‘established’ zone, or what we call the Estimated Umpire Zone (EUZ).” — Explainer at Ump Scorecards
”It’s setting the people within the game up for failure. Because catchers are getting graded one way, umpires are getting graded another way. They’re getting mad at each other because the strike zones are somewhat different.” — James McCann
“And then you’ve got a whole other group of people that are seeing the broadcast strike zone, which isn’t the same strike zone as what we’re getting graded on. So I say all that introducing the ABS challenge system is going to basically make one strike zone. … It’s going to standardize it.” — James McCann
“What worries me is the ABS zone varying from stadium to stadium. I guess that leads to a little bit of home field advantage, knowing that the strike zone plays a little higher, a little lower, a little more of the first base side, the third base side, whatever it may be.” — James McCann
“I was just curious what the shape of the strike zone was gonna look like from a digital standpoint. I just wanna make sure that the heights of the players are strictly enforced. I know in Triple-A, not all the heights were necessarily exact.” — Zac Gallen
In addition to whether the call was likely wrong, a few other considerations are the umpire behind the plate, the potential impact on run expectancy, and the impact on win probability. When all the considerations are aligned (for example umpire with 9% inconsistent calls, count is 3-2 with bases loaded, and a 1-point game), they can point to plate appearances that call for aggressive challenges.
Types of Umpires. I looked at the consistency in umpire calls compared with the Estimated Umpire Zone (EUZ) (for that game and that umpire). After looking at some of the umpires that called Diamondbacks games, there are different types of umpires:
Consistent calls at one level: great, average, and poor. An example is Derek Thomas who had very low inconsistency rates of 1.8% and 3%. Looking at the Umpire Scorecard Website, for consistent umpires the Diamondbacks can do a pre-game adjustment of the aggressiveness of their challenges.Inconsistent calls (sometimes great, sometimes average, and sometimes poor). An example is Tripp Gibson who had inconsistency rates of 1.4%, 5.3%, and 9% in Diamondbacks games. When an inconsistent umpire calls the game, the Diamondbacks can monitor the game and decide whether to adjust the aggressiveness of their calls for that game.
Run Expectancy (RE24). The possible impact of a challenge was determined by the 2024 run expectancy table in this FanGraphs article.
The following situations can be challenged with a large RE24 impact.
When bases are loaded, challenging a strike (hoping for ball four) or challenging a ball (hoping for a strikeout) could impact RE24 by at least .71 runs.With runners on first and third base, with zero or one outs, challenging a ball (hoping for a strikeout) could impact RE24 by at least .69 runs. With runners on first and second base, with zero or one outs, challenging a strike (hoping for a walk) could impact RE24 by at least .68 runs.With a runner on first, with zero outs, challenging a strike (hoping for a walk) could impact RE24 by .60 runs.With a runner on third base, with one out, challenging a ball (hoping for a strikeout) could impact RE24 by .60 runs.
When the two teams are tied or within 1 run, the impact of a successful challenge could have a significant impact on win probability. If the game is close, it becomes very important that challenge opportunities are not lost. Another situation would be when the Diamondbacks are several runs behind. Because of their above average offense, the Diamondbacks can unexpectedly score a lot of runs. For that reason, challenge opportunities should be captured, even when the team is far behind.
“Guys aren’t just gonna be challenging left and right. There’s some gamesmanship to it. Early in the game, two outs, nobody on, challenging a borderline pitch and getting it wrong costs your team a valuable challenge down the road. I think that’s gonna be interesting to see how different teams operate.” — James McCann
The Challenge System Favors Pitchers.
A perspective that is shared by Torey Lovullo and Andrew Saalfrank is that The Challenge System will shrink the strike zone. Overall, it will benefit batters. Will the smaller strike zone (instead of the larger one used in past seasons) mean that most successful challenges are by batters? My view is that the answer will depend on what run expectancy situations happen and it will depend on which umpire is calling balls and strikes.
“From a hitter’s standpoint, my generation, I feel like the pitchers had an advantage. They were getting balls off the edges of the plate. Now the balls are having to be put on the plate. I think that’s the way this rule should be.” — Torey Lovullo
“[As a pitcher], I think you benefit from not having it [The Challenge System], just getting those calls off the corners. I think it’s going to make pitching a little bit more difficult in terms of ERAs and stuff like that are going to have a whole different viewpoint to them. Statistically, I think it’s going to have a big impact on the game, just because it shrinks the small-ish zone even more for the hitters that are paid to do what they’re doing.” — Andrew Saalfrank
The Challenge System could favor the Diamondbacks in 1-run games.
This AZ Snake Pit article showed that for 1-run games, four Diamondbacks starters (Rodriguez, Pfaadt, Kelly, and Gallen) had higher call accuracy, as measured by consistency with EUZ, in wins than losses. The lone exception was Corbin Burnes. My optimistic view is that irregardless of The Challenge System, something intangible will continue to work in favor of the Diamondbacks starting pitchers.
“The catcher and the hitters were usually pretty tight on the zone. So we’re going to definitely give it to the catchers. … I’m going to just try to figure out what the best solution is to get the plays right and have the right guys call it.” — Torey Lovullo
Next season, The Challenge System will allow ball and strike calls to be challenged. It is the latest change to improve Major League Baseball.
A big question is, “Which strike zone?” Strike zones visualizations include:
the strike zone in each umpire’s head.the Umpire Scorecard Estimated Umpire Zone.the broadcast strike zone.the official strike zone. The Challenge System’s strike zone.
A critical question is, “When should each team challenge?” It goes beyond the likelihood that the call was wrong. Other considerations are the umpire behind the plate, the call’s potential impact on run expectancy, and the call’s impact on win probability. When all the considerations are aligned (for example umpire with 9% inconsistent calls, count is 3-2 with bases loaded, and a 1-point game), it is vital to aggressively challenge.
A perspective that is shared by Torey Lovullo and Andrew Saalfrank is that The Challenge System will shrink the strike zone. Overall, it will benefit batters. Perhaps most successfull challenges will be batters challenging strike calls.
My optimistic view is that irregardless of The Challenge System, something intangible will continue to work in favor of the Diamondbacks starting pitchers.