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Atlantic League to experiment with two new rule changes this season as part of partnership with MLB

The "Double-Hook DH" rule will be used for a full season, while moving the pitcher's mound back a foot will be used in the season's second half, the league says.

YORK, Pa. — Note: The video is from September 2020.

As part of their continued partnership agreement, the Atlantic League and Major League Baseball made a joint announcement Wednesday regarding two new rule changes the Atlantic League will play under this year.

The tweaks involve the lengthening of the distance between the pitcher's mound and home plate, and a new rule mandating that a team loses its designated hitter for the rest of the game when it removes its starting pitcher.

The Lancaster Barnstormers and York Revolution are part of the eight-team league, which begins its season next month. The Central PA neighbors compete in the league's North Division. 

“After a successful set of tests in the 2019 season, we are excited to introduce the next generation of experimental rules," said Morgan Sword, MLB Executive VP of Baseball Operations. "The Atlantic League is an important step in the pipeline for potential rule changes at the Major League level, and we look forward to seeing them brought to life in a competitive environment.”

Here's a look at the new rules:


The rule states that once a team’s starting pitcher is replaced, the team will lose its Designated Hitter for the remainder of the game. The Club will be required to use a pinch hitter, or the relief pitcher will bat. 

The “Double Hook” rule represents a potential compromise between the historical rules of the National League (which has not employed the Designated Hitter, except in 2020) and the American League (which has used the Designated Hitter since 1973).

Nearly 90% of pitching starts in the Major Leagues in 2020 lasted less than seven innings, the leagues said. By linking the DH to the starting pitcher, the rule aims to incentivize teams to leave their starting pitchers in longer, which in turn will increase the value of starters who can work deeper into games and increase the strategic element in the late innings of a game.   


Moving the pitching rubber back 12 inches to 61’6” will provide batters with more time to react to pitches, the leagues said. 

The expectation is that more reaction time will help batters make contact more frequently, putting more balls into play, and creating more action in the game.

The reaction time on a 93.3 mph fastball thrown from a mound 61 feet, 6 inches away from the plate is approximately equivalent to a 91.6 mph fastball (the average fastball velocity in 2010) thrown from 60-foot, 6-inch mound, the leagues said.

As pitchers have gained velocity and used technology to improve the effectiveness of their pitches, the strikeout rate in Major League Baseball has increased for 15 consecutive years, from 16.4% of plate appearances in 2005 to an all-time Major League record 23.4% in 2020, according to the leagues.

An analysis performed by Major League Baseball determined that a 12-inch increase would be the minimum interval needed to evaluate a change in mound distance, the leagues said. 

"This change is expected to be meaningful without being disruptive," the leagues said in their announcement.

The change was also determined to be safe, as it does not require the pitcher to alter pitching mechanics and there is no evidence of increased injury risk, the leagues said. 

There is also a precedent for this change, the leagues said. In 1893, the National League moved the pitching rubber back five feet, to its current distance of 60 feet, 6 inches. The result was that the strikeout rate declined from 8.5% in 1892 to 5.2% in 1893, and batting average increased by 35 points (rising from .245 in 1892 to .280 in 1893).

In 1969, in addition to reducing the size of the strike zone and prohibiting the use of foreign substances, Major League Baseball lowered the height of the mound from 15 inches to 10 inches, resulting in a 4% decrease in the strikeout rate and an 11-point increase in batting average from the previous year.

“Fans, players and many others in the baseball community have expressed an interest in seeing more regular action on the field," said Theo Epstein, former general manager of the Boston Red Sox and Chicago Cubs and now a consultant with MLB. "Therefore, it’s important that we use the 2021 season to explore various ways to create more frequent contact — and the increased action and athleticism on display that will follow.

"We are grateful that the Atlantic League — which has been at the forefront of successful rule experiments in the past — has agreed to test a 12-inch increase in the distance between the pitching rubber and home plate during the second half of the season.

"We expect to learn a great deal about the impacts of such a change and whether an adjustment to this critical field dimension is worth potential future consideration at other levels of professional baseball.”

The partnership between MLB and the Atlantic League allows baseball to experiment with prospective rule changes in the unaffiliated independent league before implementing them in the Major or Minor leagues.

A number of experimental rule changes that were first attempted in the Atlantic League have been adopted in the Minor or Major leagues. 

They include:

  • The Three-Batter Minimum, which requires the pitcher to face a minimum of three batters or complete an inning before being removed from the game and became a Major League rule in 2020.
  • Automatic Ball-Strike System, or ABS, which uses pitch tracking technology to call balls and strikes, will be used in a Low-A league this season.
  • The Step-Off Rule, which will be used in High-A
  • Restrictions on defensive positioning will be used in Double-A
  • 18-inch bases will be used in Triple-A

In addition to the new rule changes, the Atlantic League will continue its use of ABS to assist the home plate umpire in calling balls and strikes, the leagues said.

This season, ABS in the Atlantic League will feature upgraded ball-tracking technology and modifications to the geometry of the strike zone in order to better match the strike zone that players are familiar with and encourage more action in the game, according to the leagues.

MLB will analyze the effects of the rule changes before deciding on potential additional modifications during the midpoint of ALPB’s 2021 Championship Season and in future seasons, the leagues said.

The experimental playing rule changes are part of a three-year agreement between MLB and ALPB announced prior to the 2019 Championship Season.

"We are pleased to play a critical role in Major League Baseball’s tests and evaluation of experimental rules," said Rick White, the Atlantic League's president. "The ALPB is a forward-thinking league, and it is satisfying to our teams and players to be leaders determining the future of our sport. We are proud to play our part conducting MLB trials and excited to see the results of the potential changes.”

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