MLB Shift Restriction Having Desired Impact In Season’s Early Stages

The picture you see above is a window to a bygone era – beginning in 2023, major league clubs are no longer allowed to station three infielders on the same side of second base. This is one of several significant rule changes implemented this season – the pitch clock has accelerated pace of play, and bigger bases and a limitation on pickoff throws have jump-started the running game.

The shift restriction – along with the simply awful extra inning “ghost” runner, which has been around for a little while now – is the one modification that I have opposed from the beginning. I liken it to outlawing the blitz in the NFL – if hitters are going to be one-dimensional, why punish defenses for holding them accountable?

Well, we’re beginning to build a bit of a sample size of batted balls, and can begin to make some conclusions about the impact of the shift restriction thus far.

First, a little bit of background regarding ground ball batting average trends in recent seasons, to get a sense for why this restriction was introduced in the first place.

2016 – .238 AVG-.260 SLG

2017 – .224 AVG-.244 SLG

2018- .218 AVG-.239 SLG

2019 – .213 AVG-.234 SLG

2020 – .207 AVG-.226 SLG

2021 – .205 AVG-.225 SLG

2022 – .208 AVG-.226 SLG

Every year from 2016-21, batting average and slugging percentage on grounders declined, as hitters pulled the ball more and defenses over-shifted in the infield more often in response. In 2022, grounder production bounced upward slightly to just above the 2020 COVID-19-shortened season level. What gives thus far this season?

2023 – .215 AVG-.236 SLG

An increase, but not an extreme one. Grounder production now sits at between the 2018 and 2019 levels, and no one appears to be complaining. It has not changed the fabric of the game, as some feared.

But this isn’t all, or even the majority of the impact that the shift restriction has had on the game. Let’s take a similar look at production on line drives over the same time frame:

2016 – .658 AVG-.870 SLG

2017 – .653 AVG-.873 SLG

2018 – .653 AVG-.861 SLG

2019 – .649 AVG-.855 SLG

2020 – .649 AVG-.827 SLG

2021 – .644 AVG-.825 SLG

2022 – .641 AVG-.817 SLG

Let’s take a quick step back here. I’ve used the Baseball Savant batted ball database to come up with this data. A “ground ball” is defined as any batted ball with a launch angle lower than +5 degrees. A “line drive” is defined as any batted ball with a launch angle from +5 to +19 degrees.

Batting average on line drives declined consistently over that time frame, but even more significantly, slugging percentage on liners plunged. Infield over-shifts weren’t just taking singles away, largely from lefthanded hitters, they were taking extra base hits away. A big chunk of the decline in production on liners happened quite recently, from 2020-22.

What has happened thus far in 2023?

2023 = .668 AVG-.866 SLG

That’s a pretty massive one-year turnaround, pretty much matching 2016’s production on line drives, the recent high point.

This is where I’ll cut in to say that there is more than the shift ban at play here – the ball being used thus far this season seems to be juiced a bit, at least compared to the most recent seasons.

Thus far in 2023, 0.7% of line drives have resulted in home runs (14 of 1885 liners through games of April 11). In all of 2022, only 91 line drive homers – or 0.3% of all liners (91 of 27,110) – were hit. A chunk of the increase in SLG on liners is attributable to the ball, while the remainder can be assigned to the shift restriction.

Overall, offense is up a bit in the season’s early going, for a variety of reasons, with unseasonably warm April weather in much of the country joining the aforementioned causes.

If the current trends persist, my original strong concerns regarding the shift restrictions may have been overstated. No, I’m not particularly happy with lefthanded dead-pull hitters being reward for their one-dimensional ways, but I do believe that hitters should be rewarded for hitting line drives, whether they’re pulled or not. This one rule change has overnight made up the .017 of batting average and the bulk of the .053 of slugging percentage wiped out by over-shifts going back to 2016. It may not be a cause worth celebrating, but it’s certainly one worth accepting.

Next week, I’ll do a bit of a deep dive on some of the game’s lefthanded hitters most affected by this rule change, and whether they’ve taken advantage in the early stages of the 2023 season.