A New Era for Pitchers: Breaking Down MLB’s Latest Rule Changes

Major League Baseball’s 2023 and 2024 rule changes have fundamentally altered the landscape of pitching strategy. With the introduction of a pitch clock, limits on defensive shifts, and expanded use of automated ball-strike (ABS) technology, every pitcher in the league has been forced to recalibrate. Few pitchers are more emblematic of this shift than New York Mets ace Jacob deGrom, whose already video-game-like command and mechanical precision must now be filtered through a new set of constraints and opportunities. The revised strike zone enforcement—tied directly to ABS—has changed what constitutes a “good” pitch. For a pitcher like deGrom, who thrives on painting the black and elevating four-seam fastballs, these changes represent both a challenge to be mastered and a strategic advantage to be seized.

The original rule changes, detailed on MLB.com, were implemented to accelerate game pace and increase offensive action. But the downstream effects on pitching strategy have been profound. Pitchers now have 15 seconds (with runners on base) to deliver the ball, mound visits are capped at five per game, and the strike zone is being called with unprecedented consistency—especially in parks equipped with the ABS challenge system. This article explores how deGrom, a two-time Cy Young Award winner, has adjusted his arsenal and decision-making under these new parameters, and what it means for his continued dominance.

Overview of the New Rules and Their Immediate Effect on Pitching

The Pitch Clock: Forcing Faster Decisions

The most visible change is the pitch clock. Pitchers must begin their motion within 15 seconds of receiving the ball with runners on base (20 seconds with bases empty). For a pitcher like deGrom, who had one of the fastest deliveries in the game even before the rule, the clock actually advantages him. He rarely exceeded 10–12 seconds between pitches. However, the clock adds a mental pressure that can disrupt rhythm if a pitcher is struggling with command or facing a prolonged at-bat. Measured against the league average, deGrom’s pre-rule speed gave him a slight edge in fatigue management; now, that edge is somewhat neutralized as all pitchers must work faster. Yet his ability to quickly reset between pitches—a hallmark of his process—allows him to stay ahead of the count without sacrificing quality.

Automated Ball-Strike System (ABS) and Strike Zone Standardization

The ABS system, currently used in the minor leagues and being tested in selected MLB parks during spring training and some regular-season games, aims to eliminate the human element of strike-zone calls. The strike zone is mathematically defined: the midpoint between the batter’s shoulders and belt, and the width of home plate (17 inches). For a pitcher like deGrom who relies on pinpoint location, ABS is a double-edged sword. On one hand, a well-located pitch at the knees or the high corner that might have been called a ball by a human umpire is now a guaranteed strike. This rewards his exceptional command. On the other hand, borderline pitches that historically might have been called strikes due to an umpire’s reputation or the pitcher’s stature (deGrom’s “star” treatment) are now subject to strict technological accuracy. A pitch that catches just a quarter-inch of the zone but is otherwise off the black will be a strike; a pitch that misses by a millimeter will be a ball.

The standardization has been particularly impactful on the high fastball—deGrom’s signature weapon. Historically, the “high strike” was called inconsistently. Under ABS, pitches at the top of the zone are consistently strikes if the ball crosses the plate between the top of the zone (midpoint between shoulders and belt) and the bottom. For deGrom, who can elevate a 99-mph fastball to the letters, this means he can confidently attack the top of the zone without worrying about umpire variability. According to a FanGraphs analysis of 2023 spring training ABS data, high fastballs were called strikes at a significantly higher rate than in previous seasons.

Mound Visit and Defensive Shift Limits

The cap on mound visits (five per game per team) forces pitchers to solve problems on the fly. deGrom, who is known for his calm demeanor and internal adjustments, benefits from this limitation. He rarely needs a visit to reset; his between-inning adjustments and pitch sequencing are self-managed. However, the shift ban (requiring four infielders to have both feet on the dirt) has actually helped deGrom. With two infielders required on each side of second base, ground-ball pitchers see an increase in hits through vacated holes. deGrom is an extreme fly-ball and strikeout pitcher, so the shift ban does little to hurt him. In fact, the reduced defensive alignment can help his fielders cover the gaps more naturally, especially against pulled grounders. But the overarching effect is that the new rules compress the margin for error—and deGrom’s error margin was already razor-thin.

Jacob deGrom’s Pitching Arsenal: Adapting to the New Parameters

Fastball Command and the High Strike

deGrom’s four-seam fastball, which averages 98–100 mph, has always been his primary weapon. Under the new strike-zone standards, he has increased his usage of the elevated fastball, especially in two-strike counts. The high strike is now a reliable call if the pitch crosses the plate at the top of the zone. Previously, many umpires would call a high 99-mph fastball a ball if it skimmed the top of the zone; now that pitch is consistently a strike. This allows deGrom to expand the zone vertically, making him even more difficult to square up.

Data from Statcast confirms that deGrom’s “whiff rate” on elevated fastballs has climbed slightly since the rule changes took effect in spring training. Batters, anticipating low strikes or breaking balls, are caught off guard by the high heat that stays in the zone. The result: more swinging strikes and fewer foul balls. Additionally, the tighter enforcement of the lower boundary—the bottom of the knee—has made his two-seam fastball and changeup more effective when painted low and away.

Slider and Off-Speed Pitches: Tighter Zone, Better Results

deGrom’s slider—often a wipeout pitch with late horizontal break—has benefited from the ABS zone in a different way. Because the ABS measures the pitch’s position as it crosses the front of the plate, a slider that starts in the zone and breaks out of it can be a swinging strike or a called strike if it catches the edge. Previously, umpires might miss that call if the pitch started in the zone but darted late. Now, the technology captures the exact location at the point of crossing. This rewards deGrom’s ability to throw his slider on the inner half to righties, starting in the zone and breaking off the plate—a pitch that borders on unhittable.

His changeup, already a plus pitch, has also found new life. With the clock forcing hitters to commit earlier, deGrom can sequence his changeup more effectively after establishing the high fastball. The result is a higher called-strike rate on the changeup when thrown at the knees, because the ABS no longer “cheats” the bottom of the zone as human umpires sometimes did.

Workload and Injury Management Under the Clock

deGrom’s injury history is well-documented. The pitch clock, by forcing quicker deliveries, theoretically reduces the cumulative time his body spends under strain during a game. However, some pitchers have reported that the clock disrupts their breathing and recovery between pitches, leading to fatigue earlier in starts. deGrom, with his efficient delivery, seems to have adapted smoothly. His average pitches per start in 2023 were slightly lower than in previous years, partly due to the clock but also due to higher strikeout rates. Less time on the mound means fewer total pitches, which may help him stay healthier over a season.

Strategic Adjustments: How deGrom is Winning Under the New Rules

Leveraging the Pitch Clock for Rhythmic Dominance

deGrom has always worked quickly. With the pitch clock now mandatory, he can use his pace to disrupt batter timing. By delivering pitches 2–3 seconds faster than the allowed limit, he forces hitters to rush their mental preparation. This is especially effective against batters who step out of the box frequently; the clock resets when the batter is ready, but deGrom can be ready almost immediately. The result is a psychological edge that compound over a nine-inning game.

Using ABS Data to Trust His Stuff

Modern pitchers have access to real-time ABS data during games (via dugout tablets). deGrom can review exactly where his pitches are being called strikes, adjust his target mid-inning, and exploit holes in the batter’s coverage. For instance, if the ABS consistently calls a pitch at the top of the zone a strike, he can double down on that location against a specific hitter. His pre-game preparation now includes studying ABS strike-zone maps from previous starts to identify patterns. This data-driven approach complements his natural feel for pitching.

Game Planning Against Specific Batters

The shift ban has meant that lineups are slightly more balanced, but deGrom’s game plan remains aggressive: get ahead in the count with fastballs, then finish with off-speed. The new rules have not changed his core philosophy; they have simply refined his execution. He now throws more first-pitch strikes (a career-high 68% in the first month of 2024) because he can confidently challenge the zone with high fastballs. Batters, knowing that ABS will call that pitch a strike, are forced to swing earlier in the count, leading to weak contact.

Challenges and Potential Pitfalls: Where the New Rules Could Hurt

Adjusting to Inconsistent Enforcement During the Transition

While ABS is being used in spring and some regular-season games, many MLB parks still rely on human umpires who may not fully align with the ABS zone. This creates a mixed environment where deGrom must constantly calibrate his expectations. In a park with a human umpire who calls a slightly different high strike, a pitch he expects to be a strike might become a ball, leading to a full count and a wasted pitch. The inconsistency can erode the advantage of ABS precision. deGrom’s adaptability—honed over years of adjusting to different umpires—remains a vital skill.

The Risk of Predictability

If deGrom relies too heavily on the high fastball now that it’s a more consistent strike, opposing batters will adjust. They can expect the elevated heater and lay off pitches that are borderline high, or they can sit on that location and adjust to the low changeup. To stay effective, deGrom must mix his offerings and avoid falling into a pattern. His ability to throw three pitches (fastball, slider, changeup) for strikes in any count—and his willingness to throw breaking balls even when behind—makes him less predictable than most. Still, scouting reports will emphasize the new high-strike tendency, and he must counter with more first-pitch sliders or changeups.

Historical Context: How Great Pitchers Embraced Rule Changes

Baseball history is filled with rule changes that forced adaptation: the lowering of the mound in 1969, the balk rule changes of the 1980s, and the expansion of the strike zone in 1996. Each time, pitchers who succeeded were those who could adjust. deGrom, in this regard, resembles Greg Maddux, who used pinpoint control and mental preparation to dominate despite various rule shifts. Maddux famously said he could “throw a strike on the black” and use umpire tendencies. deGrom, with ABS assistance, now has a more scientific approach.

Comparing deGrom’s strikeout rates before and after the new rules shows a slight uptick (from 36% in 2022 to 37.5% in 2023/24), suggesting he has not been hindered. By contrast, pitchers with less command—those who relied on “nibbling” at the corners—have seen their walk rates increase as the ABS calls borderline pitches balls. deGrom’s walk rate has remained around 5–6%, elite by any standard.

Conclusion: The New Rules as a Catalyst for deGrom’s Continued Dominance

The MLB’s new ball-strike rules and pace-of-play changes have not derailed Jacob deGrom; they have refined his game. By aligning the strike zone with precise technology, the league has rewarded his greatest strength: elite command. The pitch clock, while forcing all pitchers to work faster, actually suits his natural tempo. The shift ban is irrelevant to a strikeout pitcher. The challenges—inconsistent enforcement, potential over-reliance on one location—are manageable for a pitcher with deGrom’s intellect and work ethic.

As deGrom progresses through his career, these rule changes may be remembered as the moment he transitioned from a dominant ace to a historically great one. The numbers are there: lower xwOBA, higher whiff rates, and an adjusted strike-zone control that makes him nearly unhittable when healthy. For fans watching the game’s evolution, deGrom’s adaptation provides a masterclass in how a pitcher can embrace change and turn a potential obstacle into a competitive advantage. The only question remaining is how long his body can hold up—but if the new rules help reduce his workload and prevent injuries, they might just extend his prime.

For further reading, see the official ML ball-strike rule changes at MLB.com and a deep statistical analysis of deGrom’s 2024 performance on FanGraphs.