What effect has the deadened ball had on MLB’s offenses?

Back in 2019, the New York Yankees and Minnesota Twins looked like two veritable super-teams, powered by offenses that hit the most and second-most home runs in Major League history. Just two years later, however, both squads have criminally underperformed in the season immediately following the league’s decision to deaden the ball to reduce the number of home runs.

Is it a coincidence that two teams that were extremely reliant on home runs are both having down years this season? Absolutely, as Minnesota’s problem has not been its offense, but a pitching staff that couldn’t stop tar pitch from flowing — and it flows so slowly I didn’t even realize it was a liquid until I Googled “slowest flowing liquid” just to make this analogy! But it did get me thinking — we’ve already seen studies about how the deadened ball has resulted in fewer hits and more outs (and not more doubles and triples, as was intended), but what have been the competitive implications of the deadened ball? And so, I began to dive into the numbers.

My initial theory was that teams that were more reliant on home runs have been abnormally affected, a theory actually parroted last night by the FOX broadcast team. Unfortunately, as I could not access 2021 Guillen numbers (the stat that indicates how much a team relies on the long ball to score), I had to use less precise stats. To begin, I graphed both HR/FB percentage and runs/game against hard-hit percentage.

For the most part, runs per game is down fairly regularly across the board — teams with a higher hard-hit percentage are just as affected as those with a lower hard-hit percentage. Of course, it must be remembered that the r-squared value suggests that hard hit percentage only has a 7-10 percent correlation. On the other hand, the deadened ball has distinctly affected HR/FB% rates more for teams that have hit the ball harder.

But how hard a ball is hit is only part of the equation. When we take a look at the types of contact, we see a much clearer trend.

We talk a lot about the notion that getting the ball in the air is the most important goal for a batter, while putting the ball on the ground too much is very much the opposite. And while I would not explicitly say that it’s bad to put the ball in the air, this data does suggest that fly balls are not scoring runs nearly as reliably as they had been: whereas a high fly ball percentage used to correlate fairly well with scoring a lot of runs (and a high ground ball rate the reverse), the correlation has all but vanished.

At this point, what are the conclusions that we can draw from this data? It’s probably still a little too early to make many concrete conclusions — after all, offense tends to heat up as the weather heats up, and we’ve only had a small sample of summer-like weather so far. However, the early data suggests that the deadened ball has rewritten everything that we knew about modern offensive performance.