Here's the short answer: since Opening Day 2023, MLB requires all four infielders to stay on the infield dirt, with at least two on each side of second base, and they cannot switch sides during a play. The old full shift — three infielders stacked on one side of second — is gone. The biggest measurable winners have been left-handed hitters, who faced shifts on 62% of their plate appearances in 2022 compared to 22% for righties. I'll walk through what changed, why, and what the data shows about players like Corey Seager and Kyle Schwarber.
Understanding the Traditional Defensive Shift
Before the rule change, the infield shift was a simple, logical tactic: instead of placing defenders in traditional positions, teams moved them to the side of the field where a specific batter was most likely to hit the ball. Dan Chruscinski, writing at The Batters Den, explains that the strategy was fueled by analytics — teams used "spray charts," detailed maps showing where every ball a batter hit landed, to play the odds.
The most common form was the full infield shift: three infielders, or more, positioned on the same side of second base. MLB's own Statcast glossary defines it exactly that way. If a pull-happy left-handed slugger routinely grounded out to the right side, teams simply parked their shortstop and second baseman in shallow right field and let physics do the rest.
This wasn't a fringe tactic by the end. In 2022, the final season it was allowed, MLB teams deployed an infield shift on 38% of all plate appearances league-wide. Left-handed hitters bore the brunt, facing an infield shift on 62% of their plate appearances, according to MLB's shift data. Right-handed hitters saw it just 22% of the time. The shift had become the default defense against an entire class of hitters.
The 2023 MLB Rule Changes: New Infield Positioning Requirements
In September 2022, Major League Baseball announced three rule changes approved by the league's Competition Committee, adopted after extensive testing at the Minor League level over several years and with feedback from MLB player and umpire representatives. The shift limits took effect beginning with the 2023 season.
The positioning requirements are specific. The four infielders must be within the boundary of the infield when the pitcher is on the rubber, and infielders may not switch sides — no repositioning your best defender to the side where the batter is most likely to hit the ball mid-at-bat. Per MLB's glossary, defensive teams must have a minimum of four players on the infield, with at least two infielders completely on either side of second base. ESPN's reporting on the Competition Committee vote adds that both feet must be on the dirt.
There are boundaries to the ban, though. The rule does not preclude a team from positioning an outfielder in the infield or in shallow outfield grass in certain situations, according to MLB. What it does prohibit outright is the four-outfielder alignment. So creativity survives — it's just confined to the dirt, with two fielders committed to each side of second base.
