Where have all the home runs gone? (Chris Carlson/AP)

Within the existential crisis confronting Major League Baseball over the way the modern game is played, there was always one saving grace. If the games were going to feature more pitches, more strikeouts, more walks, more pitching changes, and more all-or-nothing swings but fewer balls in play than at any time in the game’s history — all of that could be tolerated, from a fan-experience perspective, as long as there were also tons of home runs.

You could take away bits of action from the margins of the game, as long as the ultimate action — the ball flying over the fence at ever-increasing rates — was the payoff. And for the past few years, that has been the case. It doesn’t mean this version of baseball was better than the old one, but it means, even for fans who might otherwise be turned off, it was tolerable.

“I actually really like the game,” Commissioner Rob Manfred said last year. “But it’s not what I like — the issue is what do the fans want to see. [And] our research suggests the home run is actually a popular play in baseball.”

But what if all the other time- and action-sucking trends held true, but home runs started to decline? That’s where baseball is in April 2018. And just as with a slumping slugger or a struggling pitcher, while it may be too early to panic, it isn’t too early to worry and wonder whether there’s a problem.

Through the first 3 ½ weeks of the season, strikeout and walk rates have increased over March/April 2017 — with strikeouts accounting for 21.6 percent of all plate appearances last year and 23.0 percent this year (through Thursday), and walks increasing from 8.7 percent to 9.2. That puts the game on a pace to set a record for strikeouts for a 12th straight year and produce an 18-year high for walks. No surprises there.

But the home run rate, which has been on a precipitous climb since the middle of 2015, is down so far this season, from 2.34 homers per game in March/April 2017 to 2.14 per game so far in 2018. A nine percent drop may not seem like much, but over a full season, that comes out to more than 600 fewer homers than last year’s all-time-high total of 6,105.

This was not an expected outcome in 2018, especially after home run rates were up again across the sport this year in spring training. So far in the regular season, batters are still hitting fly balls at the same rate as in March/April 2017 – 35.6 percent of all batted balls – but the percentage of those fly balls turning into home runs has dropped by a full point, from 12.8 percent to 11.8.

There are, of course, extenuating circumstances, namely the unusually inclement weather across the eastern half of the country this month, which has led to a near-record total of postponements and may have also contributed to the lower home run rates. Fly balls typically leave the park more frequently as the weather heats up.

But various scientific and journalistic studies last year — as well as the anecdotal evidence provided by Justin Verlander and others — found that changes to the composition of the baseball itself were responsible, at least in part, for the surge in home runs. And given this season’s drop, speculation has already begun that another change to the ball has swung the pendulum back in the other direction.

This season, MLB mandated that all teams store their baseballs in air-conditioned rooms, while the Arizona Diamondbacks for the first time are using a humidor at Chase Field to store theirs. Both measures were intended to standardize the baseballs’ “coefficient of restitution” — or, their liveliness. The Diamondbacks’ humidor has served its purpose, as the home run rate at Chase Field has dropped acutely, from 3.5 percent of all plate appearances in 2017 to 2.7 so far this season. Perhaps the air-conditioned storage across the game is having a similar, if smaller, effect.

Alan M. Nathan, professor emeritus of physics at the University of Illinois and a leading expert on the physics of baseball, is among those who caution against jumping to any conclusions, about either home run rates or the composition of the baseball, at this early date.

This year’s decline in homers “might be due to the unusually cold weather,” Nathan in an email. He added, “I am generally skeptical of claims that the ball has changed, whether ‘juiced’ or ‘unjuiced.’”

Today’s version of baseball is different than any version that came before: increasingly, an all-or-nothing proposition in which, in 2017, more than a third of plate appearances (33.5 percent) resulted in either a walk, a strikeout or a homer. That’s the highest rate of “three true outcomes” and the lowest rate of balls in play in history.

We all seem to have decided we can sacrifice a certain number of dazzling defensive plays for the sheer spectacle of a lineup full of 20-homer hitters. (In 2017, in fact, 89 of the 144 hitters with enough plate appearances to qualify for the batting title hit at least 20 homers, the highest percentage in history.) We have learned to embrace the 200-strikeout slugger, as long he also produces 50-plus home runs, as Aaron Judge did last year.

The problem for the sport comes when the recipe for all-or-nothing baseball becomes too heavy on the nothing, and too light on the all.

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