How Acuña is bucking MLB's strikeout trend

Ronald Acuña Jr. is hitting .327/.424/.702, leading or tied for the lead in the Majors in runs and home runs, and so you immediately know he’s on another level, which is impressive enough in itself considering that he was already off to one of the most incredible career starts in baseball history.

Maybe that’s just the inevitable progression of a wildly talented player who only turned 23 years old in December. Maybe it’s just a well-timed hot streak to start the season. Most likely, it’s a little bit of both. But it’s also this: What if, by turning a weakness into a strength, Acuña is forcing pitchers to do exactly what he wants them to do, something that goes against the changing nature of Major League Baseball? What would that look like? Let's go on a journey.

This particular trip starts here: As the rest of the sport is striking out more, Acuña is striking out less. A lot less. That's a decline from last year's 30% rate to this year's 13% strikeout rate, which is the third-largest drop in baseball.

That's largely attributable to a massive improvement in plate discipline, as MLB.com's David Adler recently delved into, and Acuña currently has the fourth-lowest chase rate in baseball. It's a lot easier to make contact when you're not going after the pitches that the pitcher wants you to go after, obviously.

But, as Adler further went into, a lot of this is specifically about non-fastballs. That is, Acuña has managed to lay off breaking pitches and offspeed pitches outside of the zone to an extent he's never been able to do before. Most years, he swings at about one-third of those kinds of pitches outside of the zone, to relatively little success (.170 average/.250 slugging/38% strikeout rate). This year, he's gone after just 21% of breaking balls outside the zone and 10% of offspeed pitches. Only a handful of batters who have seen at least 50 of those pitches have gone after them less often.

So, because Acuña is doing a better job of not swinging at those low-probability non-fastballs, the ones he does swing at are far more productive. No one (minimum of 100 seen) has done more damage on non-fastballs, and it's not close. No one has slugged better. Only four players have struck out less against them; of them, two (Luis Arraez, David Fletcher) are low-power contact hitters, and one (Charlie Blackmon) plays in Denver, where those pitches don't move the same way anyway.

So Acuña is laying off bad pitches with spin, the kind of pitches the pitcher wants him to go after, and because of this improved discipline, he's able to hit them better and strike out less.

That's a fantastic way to have a great season, but it's also not the end of the tale. Pitchers, obviously, are taking notice of this. Look how they're attacking him, or perhaps more accurately, not attacking him: They're not throwing him breaking pitches as much. Hardly ever, in fact. Less than almost anyone.

This, really, is it. This is the trick he's pulling. He's seeing so little breaking stuff that of the 258 players to have seen 250 pitches, only two players are seeing fewer breaking balls -- and one of them is Cavan Biggio, who has demonstrated a near-total inability to hit fastballs so far this year.

That, of course, is not Acuña's problem. He's always mashed fastballs, and he continues to do so. Just look at what he did to this four-seamer from poor Trevor Williams in Atlanta on April 27.

But because Acuña's proved he will not go after the breaking pitches anymore, pitchers aren't throwing them as often, because he is absolutely hammering them.

In fact, if you look at every hitter in the game who's had at least 30 plate appearances end both on fastballs and not-fastballs, splitting the difference in the production between them, you'll see that overwhelmingly, they do better against fastballs. Only a handful are showing better performance in the other direction, and the few with a more extreme split than Acuña -- like Didi Gregorius or Mike Moustakas -- aren't performing at anywhere near the same level.

Because of all this, he's seeing more fastballs, and he's seeing more offspeed pitches -- primarily changeups and splitters -- which, somehow, he's yet to strike out against -- and overwhelmingly, if you asked a hitter if he'd like to see more fastballs, he's likely to say "yes, please, as soon as possible."

Acuña, therefore, has forced pitchers to do what they don't want to do -- throw fewer breakers -- which is the entire point of much of the pitching revolution that has pitchers thinking spin-first.

That really goes against the entire grain of pitching strategy in the Majors these days. There are a few reasons why strikeouts keep going up and up, but the two largest ones are that fastballs keep getting thrown faster at the same time they are being thrown less often. There's no such thing as a "fastball count" anymore, and pitchers aren't worried about "establishing their fastball" like they used to. Instead, it's more pitches with increasingly more spin, created in laboratories to move as much as possible and avoid the barrel of the bat. It's not about soft contact; it's about no contact. (To cherry-pick an example here, Clayton Kershaw allows a .312 average when batters make contact ... and a .000 average when they do not.)

Overwhelmingly, breaking balls are the pitches that generate those swings and misses. Acuña isn't just doing a better job of laying off the ones he can't hit, though he's doing that too; he's forcing pitchers to barely throw them to him anymore. It's quite the trick.

The best hitters, the truly great ones, figure out their weaknesses and try to turn them into strength. We talked about this for some time in the early part of Mike Trout's career, that he had a hole against high fastballs. He fixed it, just in time for high fastballs to become extremely popular. There aren't too many hitters you can put in a paragraph with Trout with a straight face. Acuña, it's becoming increasingly clear, is one of them.