Atlanta Braves star right fielder Ronald Acuña Jr. is one of the most complete players in Major League Baseball (MLB) this decade. He has power, speed and a strong defensive arm, but his defense in right field is sometimes rated more highly than the underlying numbers suggest.

That does not mean Ronald Acuña Jr. should be labeled a poor defender. He is, in fact, a capable right fielder with one of the strongest and most accurate arms in the game. Many consider his defense to be elite, however, and that is where the evaluation becomes more complicated. His range has been limited, although his elite athleticism and speed have often helped him overcome that limitation. The problem is that his raw speed does not always translate into exceptional coverage of the outfield.

Acuña's explosiveness has been far more impactful offensively and on the basepaths than it has been as a defensive tool. For an outfielder, the initial reaction is critical, and while the Venezuelan can still cover plenty of ground, he has not consistently shown the first step and ball recognition that define the game's best defenders. At times, his routes can be less efficient. Elite outfielders often make difficult plays look routine because they anticipate where the ball is going before it is fully in flight.

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The metrics behind Ronald Acuña Jr.'s defense

According to Statcast, Ronald Acuña Jr.'s initial reaction has never been one of the strongest parts of his defensive profile. Early in his MLB career, he was actually below league average in that area: -0.4 feet in 2018, -0.5 in 2019, -0.9 in 2020 and -0.2 in 2021.

What allowed him to compensate was his explosiveness. Even when he lost ground because of a slower initial reaction, he had the acceleration to make much of it back, making the issue less noticeable.

That changed after Acuña suffered a torn ACL in 2021. His defensive numbers in that area have declined further: -1.1 in 2022, -0.9 in 2023, -1.7 in 2025 and -1.5 in 2026 in reaction, while his burst has also fallen, registering -1.0 in 2022, -1.0 in 2023, -1.9 in 2025 and -2.1 in 2026.

In other words, Acuña is not only giving up ground with his initial reaction; he is also having more difficulty recovering that ground through acceleration. His OAA numbers reflect the broader trend: he totaled +5 OAA from 2018-21, compared with -36 OAA from 2022-26.

The change is also evident in his three-second burst. Acuña covered 33.5 feet during the first three seconds after contact in 2018. By 2025, that figure had dropped to 31.0 feet — a meaningful decline for a player whose athleticism once helped mask his defensive limitations.

Acuña's routes and arm strength remain strengths

Routes have not been a major issue for Ronald Acuña Jr. This season, he has posted a +0.6 in Route, despite registering -1.5 in Reaction and -2.1 in Burst.

The injuries he sustained in 2021 and 2024 cannot be ignored when evaluating his defense. The explosiveness that once allowed him to compensate for a slower first step is simply not at the same level it was earlier in his career.

That has been particularly noticeable on balls that require him to move back toward the wall. In 2026, Acuña has struggled on those plays, including a -7 OAA and -6 in the corresponding measure on balls hit behind him: Back Left (+2 OAA), Back (-1 OAA) and Back Right (-3 OAA).

His arm, meanwhile, remains special.

Acuña is averaging 95.1 mph in Arm Strength this season and has accumulated +2 rARM. The raw power of his throwing arm is elite. Last season, he even recorded a throw of 104.9 mph.

Still, those tools do not completely erase the deficiencies in his range and initial reads. Elite defenders maintain an extraordinary level of consistency, and that has not always been the case with Acuña. His defensive performance has fluctuated from season to season and even from one stretch of games to another, according to his Statcast profile.

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Ronald Acuña Jr. can still make spectacular plays in the outfield

Acuña's speed and powerful arm still give him the ability to make spectacular plays in the outfield. But highlight-reel moments alone should not lead to an elite defensive grade.

At times, Acuña can make a routine play look difficult because he gets a late start on the ball. That has ultimately hurt his defensive value. In 2026, Statcast has him in just the 19th percentile in Fielding Run Value, while he remains in the 96th percentile in Arm Strength.

His sprint speed has also declined from the elite levels he reached earlier in his career.

The most likely outcome is that Ronald Acuña Jr. continues to be a somewhat inconsistent defender in the coming years. His arm remains an extraordinary weapon, but the biggest question is how much of his acceleration, first-step quickness and ability to cover ground he can regain.

If his knee remains healthy, Acuña could eventually settle into the profile of an average right fielder — a player whose defensive limitations are offset by an elite throwing arm and significant offensive value.

Still, for Braves manager Walt Weiss, Acuña's arm remains an exceptional asset.

In a recent game, the Venezuelan threw out his countryman Luis Lara of the Milwaukee Brewers at second base with an explosive throw. After the game, Weiss emphasized just how special Acuña's arm is.

“Probably the best arm in the outfield … We've seen him do it several times. It's not just the strength, but the accuracy. It's a phenomenal throw,” Weiss said in comments to the media.