I Was Very Wrong About One Aspect of the Ban on Infield Shifts Last Year

One of my predictions about the new rules that took effect last season was that we would see more hits than in previous years, not just on scalded line drives off the bats of left-handed hitters, but from righties, too. I expected that, with second basemen unable to swing to the left side of second and shortstops forced not only to play a step closer to the middle of the diamond but to stay off the outfield grass (where many of them used to position themselves against hard-hitting or slow-footed righties), we would see a few more balls sneak through, but also that more batters would reach on infield hits or errors.

I was way, way wrong. Rob Mains broke down the effects of the rules changes (including the shift ban) in Baseball Prospectus 2024, and one of his fascinating findings was that the increase in BABIP throughout baseball in 2023 was not confined to grounders (liners and even fly balls also turned into hits slightly more often), but was confined to left-handed batters. Righties saw virtually no change in BABIP on grounders or liners, and only a small bump on fly balls. 

As I read Rob's excellent essay, I immediately thought, "Ok, but that doesn't account for errors. There were, surely, more errors." There weren't.

On the contrary, on pulled ground balls by right-handed batters, the Out Rate (1-((H+ROE-HR)/Balls in Play)) was 76.4 percent, the highest for the 20-plus years for which we have good data on batted ball trajectory and direction. The league's aggregate fielding percentage was the highest it's been in that time. Despite fielders theoretically having to move five or six steps instead of three or four more often, and despite having their range cut down by half a step because they can't play as deep and have to account for a greater distance between themselves and either their teammate or the foul line, we saw the left sides of big-league infields play better than ever in 2023.

Next, I checked to see whether there was a change in the quality of contact the league made. Maybe righty batters, who never have had as strong an incentive to use the whole field as lefty ones, hit weaker or bouncier grounders (ones with launch angles south of about -8 degrees, where expected BABIP begins to plunge because even hard-hit balls are two- or three-hoppers), or otherwise had lower expected value on them. Nope. Albeit by an infinitesimal amount, the league's righties hit harder pulled grounders and had a higher probability of hitting them 95 miles per hour or harder than in any previous year of the Statcast Era. The launch angle was the same. 

Based on exit velocity and launch angle, the expected singles rate of right-handed hitters' pulled grounders last year was 21.9%, the highest on record. The actual singles rate was 17.7%, the lowest on record. Go figure. Contact just as good against theoretically suboptimal infield alignments produced, if anything, worse results than in the past.

I like being wrong, sometimes. Being wrong means learning something, and baseball is one of my favorite things to learn about. We can't say anything for certain here, and we shouldn't rush to overstate these effects, but I think we just learned that shifts against right-handed batters were only hurting team defense, anyway. Maybe that was because too many weak-armed second basemen were being asked to make backhanded plays on the far side of second base, even if they were mostly ones that should have been routine-looking. Maybe there was discomfort or miscommunication between the middle infielders in their interactions on the left side of second that was absent when the shortstop made the move in the opposite direction, because the angles at which they'd move toward each other on balls hit between them were so different and their relative depths had to be much more similar than on the right side. Maybe third basemen were being needlessly marginalized by the pinch of the shortstop covering the hole with the shift on.

Any way you slice it, it's a fun finding. It might also give us a bit more confidence in Christopher Morel, as he fights to make up for what figure to be way too many errors early in his trial at the hot corner. We did just see Nick Madrigal have a defensively superb season in 2023, and this could be part of the reason. The circumscription of positioning didn't erase the major strides the league has made in identifying the best places for each fielder to play against each batter; the left side of every infield might have benefited from being in great position even after a rule came in forcing them to be a bit less algorithmically perfected than in the recent past. If it can work for Madrigal, maybe it can work for Morel, too.

On the flip side, one thing the Cubs need to take away from this is to ensure that their righty batters are pulling fewer ground balls, period. They had the eighth-most such batted balls in MLB in 2023, which is no recipe for success. Swanson hit 118 grounders to the left side, 11th-most in MLB among righty batters, and Nico Hoerner hit 110, 15th-most. Combined, the two hit just .215 on those batted balls, so it's not like either specializes in blasting one-hoppers through the hole. Hoerner, of course, does much of his best work when he uses the opposite field. Swanson simply has to drive the ball in the air more often; his 44.1% ground-ball rate was the highest he'd posted since 2018.

We could still see some of this change. With the effects of the pitch clock on baserunning and the increasing value of defensive range, we're going to see the league get faster over the next half-decade. A version of MLB with more speedy right-handed batters could be one that finally makes life hard on trapped left-side infielders. The margin for error could shrink so much that it does finally start forcing guys to play a step too shallow, or to rush throws. So far, though, banning the shift has only made shortstops and third basemen better. 

Research assistance provided by TruMedia.