While the 2021 season to date hasn't gone entirely swimmingly for the Atlanta Braves, their best player -- super(duper)star outfielder Ronald Acuña Jr. -- has never been better. Given the 23-year-old's prior excellence, that's saying something.
Speaking of his prior excellence, Acuña entered the 2021 campaign with a career slash line of .281/.371/.538 with 42 home runs and 32 stolen bases per 162 games played. At the plate, that comes to an OPS+ of 132. OPS+ is OPS adjusted to reflect league and home ballpark contexts, and each point more than or fewer than 100 marks 1.0 percent movement away from the league average. In Acuña's case, he was 32 percent better than the league average through the first three seasons of his MLB career. That's an excellent figure, especially for a player so young and especially given that he adds major value in the field and on the bases.
So far in 2021, Acuña has thrived by even his own high standards. At this writing he's batting .302/.399/.651, and he's tied for the MLB lead in home runs at 12. That line also represents an OPS+ of 172 -- again, thriving by his own standards.
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What's doubly encouraging for Acuña and the Braves is that this new, higher level is looking sustainable. Yes, it's just the middle of May, and as such it can be hazardous to draw firm conclusions based on individual performances. In Acuña's case, however, the strength of his production is underpinned by metrics that become meaningful pretty early and suggest that he's here to stay at this new level, at least for a while. Specifically, he's thriving like never before when it comes to hitting the ball with authority and demonstrating a command of the strike zone. Consider:
- Acuña's average exit velocity of 94.4 mph is significantly better than his previous career-high of 92.4 mph. Both are elite figures.
- In terms of barrel percentage, which is how often a batter hits the ball with the ideal combination of exit velocity and launch angle off the bat, Acuña's at 19.4 percent. His previous career-high was 16 percent.
- His hard-hit percentage of 58.3 is better than his previous career-high of 57.
- This season, he's hit the ball on the ground just 29.6 percent of the time. His previous career-low was 36 percent.
- As great as his 2021 slash line is, his batted-ball indicators are so otherworldly that he's actually been a bit unlucky at the plate. His expected (or deserved) batting average right now is .331 versus his actual batting average of .302. More telling is that his expected slugging percentage is .700 (!) versus his actual mark of .651.
- Related to all this is the fact that Acuña has taken a step forward in his plate discipline. He's swung at pitches outside the strike zone just 16.3 percent of the time, which puts him in the 96th percentile among MLB hitters. The other half of that is that he's swinging at pitches in the strike zone at rates higher than his pre-2021 career norms.
- Elsewhere on the plate discipline front, Acuña ranks in the 83rd percentile of K%, which is the percentage of plate appearances that end in a strikeout. His previous career best? In his rookie season, he finished in the 20th percentile of K%. There are leaps forward and then there are "Jonathan Edwards triple jump" leaps forward. This is a towering example of the latter. Considering Acuña is a frontline power hitter, you expect the strikeouts, but this season he's giving Atlanta the home runs without sacrificing contact.
- In terms of swings and misses, Acuña is enjoying a similar trajectory. He's right now in the 83rd percentile when it comes to whiff% -- i.e., among the very best. His prior career best came in his rookie campaign of 2018, when he was in the 33rd percentile. This, again, constitutes a "Jonathan Edwards triple jump" caliber of progress and growth. For a 23-year-old power hitter to swing and miss so rarely given the current league environment is an elusive feat.
So how do you parry a hitter who's doing this? You don't, really. Before the HTML flows like A.J. Puk's bygone locks, let's explain what you're about to see.
We're about to briefly turn to an advanced metric called expected weighted on-base average (xwOBA) to give you an idea of how Acuña this season is faring against the three categories of pitch types. XwOBA grows out of wOBA, which assigns proper value to every possible offensive event that happens while a batter is at the plate. Those proper valuations of singles, doubles, homers, walks, etc., distinguish wOBA from more traditional measures like AVG, OBP, and SLG. Also, for simplicity wOBA is scaled to look like OBP, which means that, say, .400 is elite and .290 is pretty poor.
All of that brings us back to xwOBA, which is an estimation of what a hitter's wOBA should be based on things like exit velocity off the bat and launch angle. XwOBA attempts to strip away luck -- bad or good -- and defensive play from wOBA and identify a hitter's baseline skill. It's useful for getting an idea of how a hitter figures to perform in the near-term future and, across a larger sample, his true skill level.
Now have a look at Acuña's xwOBA against those pitch families in 2021:
|Pitch category||2021 xwOBA||2021 average exit velocity|
For some context, the average MLB hitter has an exit velocity of 88.3 mph, so Acuña is well above that line no matter what offering he gets. As you can see by those xwOBA figures above, he's beyond elite when it comes to fastballs and breaking balls, which account for the vast majority of pitches. Sure, you can bring him down to "merely" very good status with the well-timed and well-placed changeup, but even among major-league moundsmen that pitch is often more easily imagined than actualized. So the secret to getting 2021 Acuña out is to throw him the most difficult pitch to command, and even if he's not sitting on it there's still a fair chance he'll thwack and or thwock it. Pity the twirler who faces him these days.
On another level, Acuña is the kind of player to make these kinds of miracles happen. While Acuña was not among the most ballyhooed of signees in his international class of 2014 (he signed for just $100,000), he hurriedly found a higher plane upon becoming a pro. He became a consensus top-100 prospect at the age of 17, and coming into the 2018 season he was the acknowledged top overall prospect in the game. He tore apart the Double-A Southern League as a 17-year-old and kept it up in Triple-A. Acuña also cracked the majors as a 20-year-old, and doing that -- achieving the highest level at such a ripe age -- is itself a harbinger of future greatness.
Acuña achieved that greatness before 2021 came along, and this season he's raised his own standard. Things could change, yes, but right now this higher evolved Acuña -- the one who hits the ball harder than ever while simultaneously being more selective than ever -- looks like he'll be around for a while.