Ronald Acuña Jr.’s Bat Is Nearly All the Way Back, but the Rest of His Game Lags

When the Braves won the World Series in 2021, Ronald Acuña Jr. was a bystander, as a torn anterior cruciate ligament in his right knee knocked him out for the second half of the season and the entire postseason. He returned to action near the end of April last year, but while he was the Braves’ second-most valuable outfielder — which wasn’t saying much due to the slumps and calamities that befell the team’s other fly chasers — his performance was far short of the high standard he’d set since debuting in 2018. With a strong start to his 2023 season, Acuña is showing signs of recovering his pre-injury form, though his performance in a couple of areas does raise concerns.

After hitting a sizzling .283/.394/.596 (157 wRC+) in 82 games before tearing his ACL in 2021, Acuna dipped to .266/.351/.413 (114 wRC+) in 119 games last year. It wasn’t a bad performance; his wRC+ ranked among the top 30 of all outfielders, and his 2.1 WAR prorates to about 2.6 per 650 PA. On a team where all of the other outfielders besides rookie Michael Harris II — namely Travis Demeritte, Adam Duvall, Robbie Grossman, Guillermo Heredia, and Eddie Rosario — netted -1.1 WAR, Acuña’s contribution wasn’t an unwelcome one, helping the team win 101 games. Yet his season was well shy of the elite level that he set for himself pre-injury, with a 140 career wRC+ and 6.0 WAR per 650 PA. After all, this is a player whom Dan Szymborski had once projected as the most likely to supplant Mike Trout as the game’s best in terms of WAR.

Acuña missed his chance for that, but he’s still just 25 years old, and through the first two weeks of the season, he’s hitting .370/.452/.537 through 62 plate appearances. Already he has three three-hit games and four two-hit games under his belt, and he’s helped the Braves jump out to a 9-4 record even while dealing with numerous injuries to their rotation and lineup.

While he only has two homers, Acuña is hitting the ball about as hard as he was just before getting injured:

The sample sizes are important to note here and throughout this piece — a refrain we’ll be singing for awhile, but an important one. With 44 batted ball events, we’re just past the 40 at which exit velocity stabilizes, and approaching the 50 at which barrel rate does so, so it’s reassuring to see that Acuña is roughly in between where he was in 2020 and ’21 on the latter front, and well ahead of last year.

More out of character are Acuña’s high groundball rate, groundball-to-fly ball ratio and average launch angle. He set career highs in the first two of those categories last year, and a career low in the third, and via his early performance, he’s on track to surpass those. However, groundball and fly ball rates don’t reach the point of stabilization until 80 batted ball events, so these measures are noisier at this juncture than exit velo and barrel rate; hard-hit rate doesn’t stabilize until 80 BBE either.

Even with that high (but perhaps more transient) groundball rate, it’s interesting to note that so far, Acuña’s expected slugging percentage is even ahead of his 2021 numbers:

In looking at this, it’s worth noting that Acuña fell 73 points short of his xSLG last year, the second-largest shortfall of any qualifier; notably, he was four home runs short of his Statcast expected total, the 12th-largest shortfall.

A look at his rolling xSLG shows that Acuña had stretches last year where he was hitting the ball as hard or even harder than now but couldn’t sustain that clip for very long, and even slumped to the point of being well below average. One of those valleys from last year matches up with his July, during which he hit just .219/318/.281 and had a 5.4% barrel rate; from July 10 to August 3, he went nearly 17 full games (48 BBE) without barreling a single ball.

Batting isn’t the only dimension of Acuña’s game, of course; this is a player who stole 37 bases to go with his 41 homers in 2019, the only season in which he’s played more than 119 games. While last year’s 29 steals (in 40 attempts) represented his highest total since then, he only played 46 games in 2020 and 82 games in ’21. He does lead the NL with six steals, putting him on pace for 75 over a 162-game season — wouldn’t that be a thing to see? — but his Statcast metrics show that he’s not only notably slower than before his injury, but slightly slower than last season:

On an age and percentile basis, Acuña’s relative standing has improved compared to 2022, and he’s still well above average, but his raw numbers are down a hair, which doesn’t exactly make the case that he’s all the way back.

If Acuña remains fast enough to be a force on the basepaths, where he’s really lost ground is on defense. Not only is he no longer a center fielder — he played just 13 innings there pre-injury in 2021, and just one inning since — but his right field metrics are a bit ominous. He made just 88 starts in right last year as well as 27 at DH, and while his 0 DRA and -0.7 UZR make the case that he was average, his -5 RAA paints a different picture. His jumps were poor (19th percentile), his catch percentage was four points below expected (87% vs. 91%) and while his arm remained elite (100th percentile), his -7 OAA was in the sixth percentile, outranking only Nick Castellanos and Juan Soto among right fielders. Yikes. His biggest weakness was that he was four outs below average in moving laterally towards the first base side. The Braves did have Acuña playing deeper than before (an average of 298 feet vs. 290 in ’21), which might have been an issue, and he was playing with a new center field neighbor in Harris, who was above average (6 RAA) and strong in both directions laterally — but then his 2021 center fielders (usually Cristian Pache and Heredia) were above average as well.

Still, don’t try to run on him:

For all of that, even with his defensive decline Acuña projected to produce 5.5 WAR via our Depth Charts, with more than a 60% chance of being a four-win player according to ZiPS; here’s his percentile projection, courtesy of Dan:

That’s pretty impressive, enough that he ranked 20th among all players in terms of his preseason ZiPS. Still, in noting that his performance-to-date prorates to 75 steals and 25 home runs over the course of a full season, I couldn’t help but be reminded of the legend of Eric Davis, the oft-injured outfielder whose peak is still spoken about in hushed tones by men of a certain age; in 1986, his age-24 season, he paired 27 homers and 80 steals, and then the next year 37 homers and 50 steals. Though he had several other very good seasons, the tantalizing promise of that speed-power combination eroded with his frequent injuries; in 17 seasons, he never topped 135 games played. Manny Machado recently compared Acuña to Ken Griffey Jr., but I wonder if Acuña will wind up being closer to this generation’s Davis. Griffey missed a lot of time due to injuries, albeit mostly on the back half of his career after building up Hall of Fame credentials, while Davis is a first-ballot Hall of What Might Have Been guy.

That’s a heavy thought, perhaps too heavy to place on the shoulders of a 25-year-old star two weeks into what is supposed to be his rebound season. For now, it should count as good news that Acuña has resumed being an offensive force. We’ll just have to wait and see as to whether his all-around game returns.