Ronald Acuna, Perpetually Greenlit
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Ronald Acuna Jr. unlocked a new offensive gear this year. He already had speed and power — he was only three stolen bases short of a 40/40 season in 2019, his first full season in the majors. That wasn’t an option this year, what with a 60-game slate, but what he did do is even more impressive: he started walking.
Acuna’s 18.8% walk rate was the fourth-highest in the major leagues. He drew walks at a higher rate than Carlos Santana, Joey Votto, and Mike Trout. This wasn’t some intentional walk mirage, either; it’s not often a great idea to walk the man batting in front of Freddie Freeman, and Acuna drew only two freebies all year. Instead, he came by it the regular way: he’s such a fearsome hitter that pitchers avoided the strike zone, and he started laying off more pitches that missed their mark.
That’s easier said than done — otherwise every hitter would be doing it. Acuna managed it, though. He didn’t do it magically; rather, he cut back on his swing rate everywhere. He swung less at pitches over the heart of the plate, and thinking “swing less often” let him cut back in every other region:
| Attack Zone | 2019 Swing% | 2020 Swing% |
|---|---|---|
| Heart | 78% | 73% |
| Shadow | 50% | 45% |
| Chase | 18% | 13% |
| Waste | 4% | 4% |
This newfound equilibrium presented a conundrum for opposing pitchers. Stay out of the zone, and you’re liable to put a stolen base threat on with Freeman batting next. Get too familiar, and you might get acquainted with Acuna’s 99th percentile hard hit rate. It’s a puzzle with no good answers.
Last year, Acuna had another wrinkle to his plate discipline game: he swung more than anyone else on 3-0. It was just another thing to think about: think of 3-0 as an automatic strike with the batter taking, and you were throwing batting practice to one of the best hitters in the game.
It was hard to tell if Acuna kept up his free-swinging ways in 2020, because he simply didn’t get to a 3-0 count very often. He saw only five of them all year as pitchers attacked him to avoid facing Freeman with a runner on base. He swung at two of those five, not enough data to say anything.
In the playoffs, things have gone rather differently. In only 30 plate appearances, he’s already reached 3-0 five times. It’s still by no means a robust sample, but make no mistake: it’s swing season again. He’s offered at four of those five, attempting to use pitchers’ fear of free passes against them.
How has that gone so far? It depends on how you judge it. On one hand, those four swings have produced two outs, a foul ball, and a whiff. That’s pretty bad! Missing on 3-0 isn’t terrible, because 3-1 is still a hitter’s count, but making an out? Disaster!
On the other hand, Acuna has absolutely pummeled the two balls he hit for an out, and he hasn’t swung at any pitches outside of the strike zone yet. Try this phrasing: if Acuna didn’t swing at any of the pitches he saw on 3-0 this postseason, he would have ended up with five 3-1 counts. Instead, he ended up with three 3-1 counts and put two balls in play, both of which he hit at more than 100 mph. That’s the opposite of a disaster; two great outcomes and three neutral ones.
Of course, that too is an oversimplification. Here’s the first of those hard-hit balls:
Hit that one as hard as you want; you can’t hit a ball that high and get a hit. The other one looks similar:
That one drew a delightful description from GameDay: “Ronald Acuna pops out sharply to third baseman Eugenio Suarez.” How do you pop out sharply? Get under the ball and hit it 103.4 mph off the bat, apparently.
Against Miami, it hardly mattered what decision he made. He could have swung, left the bat on his shoulder, or switched his bat for an umbrella and danced, and the game wouldn’t have been affected; a 7-0 lead in the eighth inning is silly season. Against Cincinnati, on the other hand, he was leading off an extra inning; a walk would be huge, but a game-ending home run would be too.
To put these 3-0 swings into context, I came up with a simplistic rule. It works like this: consider the first batter of a game in a contest that is exactly 50/50. A walk moves the visiting team’s win percentage to 53.5%. A double, on the other hand, moves it to 55.9%. The double, in other words, is worth 68% more than the walk; 5.9% divided by 3.5% comes out to 1.68.
Let’s consider that ratio — a double is worth 1.68 times as much as a walk in terms of win probability increase — a baseline. I don’t mean that swinging always produces a double or that taking always produces a walk. I don’t mean that players should be indifferent between swinging and taking in that situation. It’s merely a baseline.
There are obviously situations where swinging 3-0 is a good decision — in a bottom-of-the-ninth tie with a runner on third base and one out, a walk is worthless and a ball in the outfield ends things. With the bases loaded in the same situation, a walk is literally game over.
Using 1.68 as a baseline lets us put everything on a scale like that. The double/walk ratio checks in at 43.25 in the first situation; a double increases the home team’s win probability 43 times more than a walk does. In the second situation, the double/walk ratio is 1; a double is just a walk in fancier clothing.
In theory, we’d like a player to swing more often when the double/walk ratio is high and take more often when it’s low. We can put each of Acuna’s 3-0 counts on that scale to see whether he was in think-swing situations or think-take situations.
Chronologically first is this foul against Raisel Iglesias:
Falling on one knee on your 3-0 swing is probably not a good thing, but that aside, it was a good time to take a cut. Walking would bump the Braves’ win expectancy from 52.6% to 55%. Doubling would send it to 58%; a single breaks the tie after a double, while a walk needs several events in tandem. The double/walk ratio checks in at 2.25, higher than “neutral.”
Acuna’s next opportunity came later in the game; that sharp pop fly in the bottom of the 11th. It, too, comes in above neutral: our handy WPA Inquirer shows the home team with a 63.7% chance to win leading off the inning. That chance swells to 71.1% after a walk and 81.1% after a double, a 2.35 double/walk ratio. Putting a man in scoring position with no one out is a massive boon in a sudden death situation.
In the next series, Acuna again found himself leading off an inning in a tie game. This time, however, it was early and in the top of the inning rather than late and in the bottom:
Unsurprisingly, this looks almost exactly like our baseline number, a 1.7 double/walk ratio. There isn’t much difference between the top of the first and the top of the third, in other words.
Merely an inning later, he came to the plate again in a less tense situation:
This is another situation where a double is contextually better than a walk, though the four run lead makes the decision less important overall. It checks in with a double/walk ratio of 1.8, and it would have been a bit higher in a closer game. If you’re inclined to swing 3-0, it wouldn’t be a bad time to pull the trigger, but perhaps Acuna was simply looking somewhere else in the zone on that pitch.
If you thought that Acuna was simply engaging in some misguided unwritten rules obeisance, his last swing, later in the same game, put that to rest. He swung on 3-0 with a seven run lead, as seen above. There’s no point in calculating a walk/double ratio here; the Braves were already 99.7% likely to win the game, so a walk and a double are essentially indistinguishable.
That situation aside, the other four turns at bat were good opportunities to swing. It’s hardly a surprise that Acuna ends up in 3-0 counts at times when extra bases help far more than a walk; pitching teams have agency, and 3-0 counts don’t pop up at random. When a walk doesn’t harm the pitcher very much, they’re far more likely to end up behind 3-0, which means that when he’s in a 3-0 count, it’s usually good timing for a swing.
Acuna’s newfound plate discipline helps tilt the balance further in his favor. Two of the three times that he went from 3-0 to 3-1, he walked on the very next pitch. When the fail case of swinging 3-0 is still likely to be a walk, taking a hack at a juicy pitch makes a lot more sense.
The results haven’t been there yet, but Acuna is putting pitchers in a bind this postseason. There are no free pitches — throw him a cookie on 3-0, and he’ll try to hurt you for it. He’s off to a cold-ish start so far — a 43.3% strikeout rate has capped his production. That’s no knock on his 3-0 behavior, however; in those five plate appearances, he’s come away with two walks, a strikeout, and two smashed baseballs.
This is an interesting sidebar in these playoffs; no other batter has more than one 3-0 swing, let alone four. Even beyond that, however, it’s an intriguing sign of Acuna’s maturation at the plate. This regular season, he added walks to the package. This postseason, it looks like he’s melded his previous opportunistic fastball hunting with his newfound patience. Whatever the results are the balance of this year, this development is sure to put a chill down opposing pitchers’ spines. He’s hitting smarter and harder, a terrifying development for someone who was already one of the sport’s very best players.