Major league pitchers will always adjust to the gifted young hitter who enjoys early success. The next challenge for such a hitter is in turn adjusting to those adjustments. It appears the Braves' young star Ronald Acuña Jr. is doing just that in 2020.
Friday's baseball events provided us with a timely reminder of Acuña's excellence at the plate, as he tallied three home runs across a doubleheader against the reigning champs:
In a way, these three homers are Acuña's demonstrated growth at the plate writ small. Each homer came on the fourth pitch of the at-bat -- i.e., in a count that had been worked to some extent -- and only one of the three was on a four-seam fastball. This is notable because pitchers are now treating Acuña like who he is, which is one of the best hitters in the game, and Acuña is responding by being a more disciplined hitter. First, consider how pitchers are attacking Acuña in 2020:
- The percentage of straight four-seam fastballs he's seen has fallen from 38.8 percent last season to 34.4 percent in 2020.
- The percentage of first-pitch strikes he's seen has fallen from 61.4 percent last season to 54.4 percent in 2020.
- The percentage of pitches in the strike zone has fallen from 48.2 percent last season to 46.0 percent in 2020.
So that, in general terms, is how pitchers have attempted to parry the guy who hit 41 homers as a 21-year-old. Now here's how Acuña has calibrated to that prevailing change in approach:
- Most critically, Acuña has drawn an unintentional walk in 15.5 percent of his plate appearances this season. In 2019, that mark was 10.1 percent. He's never been anything like an undisciplined hitter, but it's a sign of an intelligent approach that he's ramped up his selectivity in response to pitchers' en masse decision to work him more carefully.
- Last season, Acuña swung at pitches outside the strike zone 24 percent of the time. This season, he's chasing 22.1 percent of the time. Meantime, his swing rate at pitches in the strike zone has remained roughly the same.
- We noted that pitchers are throwing a first-pitch strike to Acuña less often. Sure enough, Acuña's now swinging at first pitches less often -- from 33.6 percent in 2019 to 30.1 percent this year.
The goal, of course, is not to take pitches and draw walks. The goal is to knock the innards out of the baseball, so think of plate discipline as a means to that end.
So what happens when, like Acuña in 2020, you successfully lay off pitches designed to get bad swings and induce weak contact and instead go hunting for fastballs where you like them? Acuña in 2019 batted .269 and slugged .491 against fastballs; this season he's batting .292 and slugging .688 against hard stuff.
Yes, the sample size is small, but plate discipline indicators become meaningful pretty early. In Acuña's case, they're painting a picture of a hitter who's equipped to, yes, adjust to the adjustments.
In matters related, Acuña on the season is now batting .279/.398/.628 with eight homers in 25 games, which is good for an OPS+ of 163. Coming into 2020, his career OPS+ across parts of two seasons was 130. Acuña's base-running and fielding make him a highly valuable contributor even when he's hitting at "just" very good levels. Now, though, he's looking like he's poised for genuine greatness at the plate thanks to growing selectivity and knowledge -- of himself and of opposing pitchers. Should this early trend continue, then Acuña, still just 22 years of age, will have multiple MVP awards in his future.