The 2023 Major League Baseball season brings a wave of rules changes collectively aimed at improving the game’s pace of play and increasing action on the field.

The arrival of the pitch timer, restrictions on defensive shifts and bigger bases makes for one of the more ambitious adaptations to the rule book in the modern era.

So here’s a handy guide to understanding the new rules and why they are being implemented.

What are the new rules?
There are three, and we’ll break them down in detailed sections below.

1. Pitch timer: The length of games will still be determined by innings, not minutes. But to create a crisper pace, there will be a 30-second timer between batters and then a shorter time limit between pitches. Pitchers will be required to begin their motion 15 seconds after receiving the ball with the bases empty or 20 seconds after receiving the ball with runners on base. If they don’t, they will be charged with an automatic ball.

Pitchers will also be limited to two disengagements from the mound (i.e. pickoff attempts or step-offs) per plate appearance with a runner on base. The disengagements reset the clock.

Batters, meanwhile, must be in the batter’s box and alert to the pitcher by the 8-second mark on the clock, or else be charged with an automatic strike.

2. Shift restrictions: The defensive team must have a minimum of four players on the infield, with at least two infielders completely on either side of second base. These restrictions are intended to increase the batting average on balls in play, and allow infielders to better showcase their athleticism with great defensive plays.

3. Bigger bases: First, second and third have been expanded from 15 inches on each side to 18 inches on each side, while home plate remains unchanged. The primary reason why the bases are bigger is safety, giving fielders and runners more room to operate without colliding. But the slightly decreased distance between bases could help runners on stolen-base attempts and bang-bang plays.

When do the new rules go into effect?
They will be in effect for all of Spring Training to provide an adjustment period before Opening Day of the 2023 season. Umpires have been instructed to begin calling violations with no grace period.

Will they also be enforced during the postseason?
Yes.

Will the new rules be used in the World Baseball Classic?
No, they will not be used in that tournament.

What was the genesis of the rules changes?
As MLB sought ways to address the issue of games taking longer with reduced action, the league conducted extensive fan research to determine, in essence, the best version of baseball.

“We’ve been asking hundreds, thousands and, through surveys, tens of thousands of baseball fans and players and executives and scouts and everybody else,” Major League Baseball consultant Theo Epstein said in 2021. “And you do see some common trends in what the best version of the game means to people.”

The consensus was action, balls in play (i.e. a lower percentage of plate appearances that result in home runs, strikeouts and walks), athleticism on the basepaths and in the field and, above all else, a faster pace.

From there, MLB’s Competition Committee and Playing Rules Committee assembled a variety of different rules change ideas aimed at prioritizing the fan experience.

Why is MLB confident these changes will help?
Because all of the changes were tested in more than 8,000 games at the Minor League levels and extensively in the independent Atlantic League before their adoption at the big-league level.

What were the results of the experiments?
In 2022, nine-inning Minor League games using the pitch timer were, on average, 25 minutes shorter than 2021 games that did not have the pitch timer (from 3 hours, 3 minutes to 2:38). Stolen-base activity increased from 2.23 attempts per game to 2.81, and the stolen-base success rate improved from 68% to 78%.

The defensive shift limits contributed to an increase in batting average across the Minor Leagues from .247 to .249.

Now let’s take a deeper dive on each of the three rules, starting with the pitch timer.

THE PITCH TIMER

What is the purpose of the pitch timer? 
To reduce the dead time between pitches and create a crisper pace of play. The average time per game has consistently been at or above three hours since 2012. The goal is to provide more action in a shorter window of time, as opposed to less action in a longer window.
 
“Initially, I hated [the pitch timer],” said MLB veteran Matt Carpenter, who spent time in Triple-A in 2022 playing with the pitch timer. “I grew into liking it a lot -- to the point where I would fully endorse it in the Major League game … The big selling point is that the pace of the game is way better. It just is.”

Why does the pitch timer increase stolen bases?
Because of the mound disengagement limits placed on pitchers.

With runners on base, the timer resets if the pitcher attempts a pickoff or steps off the rubber. To prevent the pitcher from circumventing the pitch timer, as was seen in the original Minor League tests, a limit of two disengagements per plate appearance was created.

The limit is reset if a runner advances during the plate appearance, via a stolen base, wild pitch, passed ball or balk.

Here’s more on the pitch timer’s impact on stolen bases.

What happens if the pitcher steps off a third time?
If he steps off or attempts a pickoff a third time, it is treated as a balk (the runner or runners automatically advance), unless an out is recorded.

Put another way, if the third pickoff attempt is successful, it is not treated as a balk.

Does the batter have any time-outs?
Yes. One per plate appearance. Otherwise, the batter must be in the batter’s box and alert to the pitcher with at least eight seconds remaining on the timer.

What if the pitch timer reaches zero as the pitcher is in his motion? Is he charged with a ball?
No. As long as the pitcher begins his motion prior to the expiration of the pitch timer, he is not charged with a ball. Umpires will wear a device on their wrists that will buzz when the clock expires, so it will be on them to call the violation, as opposed to a horn throughout the stadium you might hear for a shot-clock violation at an NBA game.

What about mound visits or injuries? Do those count as “disengagements”? 
No. Mound visits, injury time-outs and offensive team time-outs do not count as a disengagement. 
 
Do teams still have the same number of mound visits available per game? 
They still have five. However, an added wrinkle as a result of the pitch clock is that, if a team has used up all five of its allotted mound visits prior to the ninth inning, it receives an additional mound visit in the ninth. This effectively serves as an additional disengagement.

Can anything else stop the clock?
The umpires may provide extra time if warranted by special circumstances. For example, if a catcher were to be thrown out on the bases at the conclusion of one half-inning, he could be given extra time to put on his catching gear.
 
Basically, umpires can use their best judgment to determine if the timer needs to be paused.
 
How common will pitch timer violations be?
If the adjustment in the Major Leagues plays out similarly to the Minor Leagues, there will be many more violations earlier in the season than later. In the second week in which the pitch timer was in place in the Minor Leagues last year, there were 1.73 total violations per game. By the sixth week, there were just 0.53 violations per game.
 
In other words, players adjusted in about a month.

SHIFT RESTRICTIONS
 
What is the purpose of the defensive shift restrictions?
To improve the likelihood of balls in play leading to more traditional outcomes and to showcase the athleticism of rangy defenders up the middle.
 
As a frame of reference, thanks in part to the prevalence of extreme defensive shifts, the MLB-wide batting average on balls in play in 2022 was .290 -- seven points lower than a decade earlier.
 
“I think it’s going to bring a lot of athleticism back into the game,” said Cody Bellinger of the Cubs. “These infielders are going to have to cover a lot of ground and show off what they can do, as opposed to standing where the ball is probably going to be hit. For me, as just a baseball fan, I think that’s pretty exciting.”

Can infielders switch sides? 
No. So if the shortstop is the team’s best defender, he cannot switch spots with the second baseman against a batter more likely to hit the ball to that side of second base.
 
Can an outfielder play in the infield as a fifth defender? 
Yes, a team can take a bigger risk of the batter hitting the ball the other way to a more open expanse in the outfield.
 
What is the penalty for failure to comply with the shift restrictions? 
An automatic ball.
 
Are shift restrictions subject to replay review? 
Yes, they are.
 
Can’t an infielder circumvent the rule by running across second base or into the outfield when the pitch is released? 
No. In addition to being physically difficult, such circumvention will be monitored by the umpires as a violation resulting in an automatic ball.

BIGGER BASES

What is the purpose of the bigger bases?
The primary purpose is player safety, providing more room for the players to operate around the bases without colliding into each other. This is particularly helpful on the many close plays at first base.

In the Minor Leagues, injury events near the bases went from 453 with the old bases in 2021 to 392 with the bigger bases in 2022.

How much do the bigger bases change the distance between bases? 
The distance between first base and second base and second base and third base is reduced by 4.5 inches. The distance between home plate and first or third base is reduced by three inches.

Oh, one last thing … what about the so-called “robot umps”?
Experimentation with the automatic ball-strike system -- and, relatedly, the ball-strike challenge system – will continue in the Minor Leagues in 2023, but the system is not in place at the Major League level and there is currently no timetable for it to be added to MLB games.