Why MLB May Have Just Ensured Your Team Will Score Less in 2021

Zachary D. Rymer@zachrymerMLB Lead WriterFebruary 9, 2021

Baseballs are shown in a bucket after use during fielding practice at a spring training baseball workout for pitchers and catchers Friday, Feb. 14, 2020, in Avondale, Ariz. (AP Photo/Ross D. Franklin)
Ross D. Franklin/Associated Press

Major League Baseball fans should get ready for a whole new ballgame in 2021.


As Eno Sarris and Ken Rosenthal of The Athletic reported Monday, MLB notified teams last Friday of changes to the baseball for the upcoming season. It will be lighter but also less bouncy, which could lead to a decrease in home runs.

In addition, the number of teams that store baseballs in humidors at their home parks will double from five to 10. That, too, could lower the home run rate.


What, Exactly, Is Going On with the Baseball?

When you look at a baseball, what you see on the outside is a white cowhide exterior bound together with red stitching. What you don't see is what's on the inside: a rubber-coated cork pill wound in layers of wool yarn.

According to Sarris and Rosenthal, MLB and Rawlings—the latter of which has been owned by the former since 2018—experimented with new balls between 2019 and 2020 that "loosened the tension of the first wool winding."

Per a memo sent to clubs from commissioner Rob Manfred's office, this resulted in balls becoming lighter by less than one-tenth of an ounce and also becoming less bouncy.

John Raoux/Associated Press

This isn't quite the same thing as what happened in Korea in 2019, in which the Korean Baseball Organization introduced a new ball that was both wider and heavier than the old one. That predictably resulted in a dramatic reduction of home runs.

Even still, MLB's memo made mention of an independent experiment which found that fly balls of over 375 feet with the new ball lost one to two feet in total distance.

If that were to hold true in actual games, one analyst estimated that home runs could fall by 5 percent. To use MLB's record-setting 2019 season as an example, there might have been about 340 fewer home runs that year had the new ball been in circulation.

As for whether MLB is intentionally trying to make the ball less lively, one general manager was blunt to Sarris and Rosenthal: "That’s the desired result.” 


And Now for Some Context

At first, this story might have a vaguely scandalous smell to it. After all, what we have here is MLB admitting to intentionally futzing with its baseballs after previously denying that it was doing so.

But dare we say it's actually refreshing.

One of the more consistent storylines over the last few seasons concerned how inconsistently the ball was behaving. At first, it seemed juiced. Then it seemed super-juiced. Then it was seemingly de-juiced. Then it was seemingly somewhere in between juiced and de-juiced.

Unofficially, the juiced balls may have been the result of less dense cores. Officially, the liveliness actually had something to do with seam height. But ultimately, whether the ball behaved one way or another evidently depended on which batch they were drawn from.

Complicated? You bet. And frustrating for everyone involved, up to and especially including the guys playing the games? That, too.

Mercifully, it seems as if the new balls will be more consistent. Rawlings says they're going to be centered around the midpoint of the acceptable range of coefficient of restitution (i.e., "bounciness") of .530 to .570. That could hypothetically result in less variance in their performance.

If deadening the ball is a necessary trade-off for that, well, so be it. A dent in the league's home run rate would also be a dent in the rate of the three true outcomes per game, which has exploded to cartoonish levels in recent seasons:

Data courtesy of Baseball Reference

In 2020, strikeouts, walks and home runs accounted for a record 36.1 percent of all plate appearances. Meanwhile, the average time for a nine-inning game rose to a new high of three hours and seven minutes.

In other words, games are getting less action-packed and longer. There is no magic bullet that's going to solve both problems. But if the new ball—not to mention the humidors, which have been known to reduce power—does decrease in home runs, there might be more action by way of more balls in play in 2021.

Then again, this is very much a "maybe" proposition.


What Are the Unintended Consequences?

There's more to the science of home runs than how fast the ball comes off the bat. There's also the matter of drag, or how the ball moves through the air.

To this end, Sarris and Rosenthal found no mention of drag in MLB's memo on the new balls. If that's because that element has yet to be studied, it isn't out of the question that the new balls—which, again, are lighter in addition to less bouncy—won't actually behave that differently than the old balls.

Even if they do, the notion that fewer home runs will equal more balls in play requires a hefty dose of wishful thinking.

David Zalubowski/Associated Press

The No. 1 contributor to the rising rate of three true outcomes isn't home runs, but strikeouts. To wit, each of the last 13 seasons has set a new record for MLB's overall strikeout rate.

In theory, the new ball is only going to change that if the home run rate declines dramatically enough to force hitters to change their habits. Many would have to stop praying at the altar of launch angle and adjust to become more about making contact and finding the gaps in the defense.

Is a 5 percent reduction in home runs going to do that? Almost certainly not. To once again use the 2019 season as an example, even the hypothetical 340 home run decrease would have only lowered the average output to 1.32 per game. That would still be an all-time record.

So if anything changes this season, it could involve a run-scoring environment with fewer home runs and more strikeouts. That isn't a solution. That's a new problem.

For now, this is a wait-and-see situation. And if MLB's new ball eventually does make its product materially worse in 2021, the fix would be obvious: bring back the old balls.


Stats courtesy of Baseball Reference and FanGraphs.


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