Editor’s note: Marquee Sports Network’s Katie Krall built defensive positioning models for the Cincinnati Reds during her two years as a baseball operations analyst (2020 and 2021). She also, as the Boston Red Sox Double-A affiliate’s development coach in 2022, was a conduit between the front office and the field in communicating where to station infielders and outfielders.

Defensive positioning cards have become ubiquitous in Major League Baseball as teams continue to translate data into on-field strategy. You can find these cards wedged in players’ back pockets, tucked in their hats and placed under their gloves in the dugout.

They’re the output of front-office models to optimally position players, and while infield defensive shifts has been restricted since the 2023 season, competitive advantages still can be gained from ensuring infielders and outfielders are properly deployed.

The act of coaches moving infielders and outfielders from the dugout (typically with emphatic gesturing or waving) is as old as the game itself, but teams now have tools to objectively determine that putting players in certain spots has the highest likelihood of converting batted balls into outs.

While each team has unique features to their model, all of them begin by collecting historical data on a player’s tendencies for batted balls or his spray distribution, which Hawk-Eye provides to teams and websites such as Baseball Savant make available to fans. The team’s Research and Development (R&D) department then will train models to predict the “spray” distribution of each specific hitter’s batted balls off a specific pitcher. These models include information about the batter’s and the pitcher’s tendencies, the venue the game is being played at and even the weather conditions.

Teams then use an optimization algorithm to determine players’ best defensive locations to minimize the damage a batter can do. Those locations can change given the game situation, with a context-neutral model providing ideal positioning irrespective of the base/out state and a context-dependent model taking into account such things as a double-play possibility, a man on third, a two-strike count, etc.

The final product will be recommendations for where defenders should play against each opposing batter, given the team’s pitcher, and cards are generated at the start of each series. An advance scouting analyst or coach will print and distribute them to the corresponding players.

Infielder cards typically are less prescriptive and represent suggested shading given the batter, whereas outfielder cards typically denote the number of steps to take forward/back or laterally. The left fielder, center fielder and right fielder each will have unique origin points from which the recommendations will be made, depending on the ballpark.

For example, if the right fielder is told to play three steps back against a given batter, it’s not three steps back from where he made the last out but a finite point. During batting practice at the start of a series, the outfield coach will walk the grass with players to ensure they understand the origin and pertinent reference points.

The shelf life of this information is very short, as recency is incredibly important to ensure teams have a current picture of that player’s tendencies. Therefore, the defensive positioning cards the Cubs might create for their May series at home against the Reds wouldn’t be reused for the September games in Cincinnati.

Rather than being stone tablets handed down from R&D, defensive positioning cards are most valuable when they spark conversation among players, staff and the front office. Most teams still typically empower their infield and outfield coaches to override a suggestion if they believe the model might not have captured an aspect of the player’s game or the situation.

The effect of successful defensive positioning often is subtle, as one small step can make a world of difference. Sometimes, Cubs shortstop Dansby Swanson and second baseman Nico Hoerner make excellent plays on the strength of their Gold Glove defense. Yet there also are instances across MLB when an analyst celebrates a routine play that otherwise wouldn’t have been made if that player hadn’t checked the card in his pocket.