Triple-A Strike Zone, Pitch Clock Being Tweaked For Stretch Run


Image credit: One of over 30 ABS cameras monitor each pitch for balls and strikes during a AAA minor league baseball game between the Memphis Redbirds and Lehigh Valley IronPigs at Coca-Cola Park on May 9, 2023 in Allentown, Pennsylvania. (Photo by Rich Schultz/Getty Images)

In a call today with farm directors for the 30 MLB teams, Major League Baseball laid out further tweaks to rules for the automated ball-strike system (ABS) and the pitch clock that will go into effect Sept. 5 across Triple-A baseball.

All of these tweaks will be in effect for the final month of the Triple-A season. But probably as importantly, it will provide data and player/coach feedback on how the new tweaks are viewed in advance of the upcoming 2024 season.

A New Way To Set The Strike Zone

The most significant change will be an adjustment to the strike zone. In Triple-A half of each series has balls and strikes called by the ABS system. In the other half of the series, the home plate umpire calls balls and strikes, but hitters and pitchers can challenge a call. If challenged, the ABS system determines if it was a ball or a strike.

That ABS strike zone has set the upper and lower zones of the strike zone based on percentages of a player’s height. That has led to some complaints that the strike zone didn’t always best correspond with the “human” strike zone for a hitter. Different players have different body types. One 6-foot-2 player may be very long-legged, while another could have a very long trunk. Under the height-based system, they had the exact same strike zone, even if that meant it started below the knee for one batter and ended well above the belt for another. Those strike zones also did not take into account any aspect of a player’s batting stance.

Now, the ABS system will use the Hawkeye system’s visual tracking to set the Triple-A strike zone. Since the Hawkeye system tracks each player’s limbs, the strike zone will now be set individually for each player. The system will set the bottom of the strike zone at a player’s knees. For the top of the zone, the strike zone will be set as two baseballs above the midpoint of the measurements of a player’s left and right hips. That’s aimed to put the top of the zone near the belt-line.

The new zone will mean each player’s strike zone is uniquely tied to their body and stance rather than a universal formula. The new strike zone is hoped to more closely resemble the strike zone used by human umpires, although the top end is still designed to be lower than the top end of the MLB strike zone.

That lower top end of the zone was intentionally designed into the new Triple-A strike zone to see if it would reduce the number of strikeouts on riding four-seam fastballs on the top of the zone. It has helped to reduce strikeouts by a modest amount, but in doing so it has also upped the walk rate by roughly twice the number of reduced strikeouts.

The new strike zone is expected to add back a half inch or so of the reduction in the top of the strike zone (when compared to the MLB zone) but will still have a lower top than the MLB strike zone.

Pitch Clock Tweaks

In addition to the strike zone adjustment, there will be some tweaks to the pitch clock for Triple-A as well. Beginning on Tuesday, the Triple-A pitch clock will be set at 17 seconds between every pitch. In the past, it has been 14 seconds with no one on base and 19 seconds with a runner on base. (In the majors, it’s 15 seconds with no one on and 20 seconds with runners on base).

The new 17-second rule is a response to feedback from hitters who said the switch between 15 to 20 seconds depending on baserunners was disruptive to their pre-pitch rhythm.

This is an example of a change that couldn’t happen without technology. Without the PitchCom system that allows catchers and pitchers to communicate without using signs, there would have to be more time allowed with runners on base to allow teams to run through multiple signs to thwart sign stealing. But with PitchCom now being used near universally in the majors and Triple-A, that is no longer a factor.

Two other changes will probably be less noticeable to fans and even players. The maximum number of mound visits in a Triple-A game will be cut from five to four (with an extra mound visit in the ninth inning allowed if a team has used up its allotment). This appears to be an effort to cut down on the number of times a catcher thwarts a pitch clock violation by calling for a mound visit as the clock ticks to zero.

And starting on Sept. 5, pitch clock operators will be instructed to start the pitch clock as soon as the pitcher receives a new baseball. In the past, they have been instructed to start the clock when the pitcher has the ball and stands on the mound. Some pitchers had come to realize they could delay the pitch clock start by standing somewhere other than the mound when they got a new baseball.

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