“Don’t run on Ronnie,” goes the saying around Atlanta, and it’s not hard to see why.

Among the many gifts possessed by Ronald Acuña Jr. the presumptive National League Most Valuable Player, is an absolute cannon of a throwing arm. In a perfectly satisfying case of the metrics matching the eye test, Acuña appeared at No. 2 in 2022’s list of strongest throwing arms (97.9 mph), and so far in 2023, he’s third, at 96.7 mph. His arm is so good, so strong, that he was in large part responsible for the first-week controversy that essentially torpedoed St. Louis’s season before it even began.

We can’t, at this time, account for that -- crushing the souls of a National League competitor, that is -- in any metric. But given all the information we have at our disposal with the Statcast technology, we can tell you something a little more interesting about outfield arms, and it has a whole lot to do with a play like this, where Acuña catches an easy fly ball, and then has no runner attempting to advance. It has to do with respect.

Orioles baserunner Gunnar Henderson made the wise choice to hold at third rather than challenge Acuña’s deadly throwing arm, and he’s hardly alone. This year, according to the newest Statcast metric, which puts a run value on outfielder throwing arms, Acuña has been worth +4 runs on the strength of his arm alone, the second-best mark in the game.

That is, obviously, in large part due to throwing runners out. But what's notable here is that part of what goes into this is the value in runners not even trying to test you, and for Acuña, he's earned an MLB-best +5 runs just in that regard, in "holds," in runners looking at the situation and saying: no. (Not actual scoreboard runs, of course. On each play, the actual outcome compared to the expected outcome of the opportunity is graded, and the increments add up to a season-long measure with ‘runs’ as the unit. You can read more about that here.)

Based on the opportunities Acuña has seen -- here we're talking his position in the grass, the runner's speed and position, etc. -- an average outfielder would have expected runners to advance 38% of the time. Against Acuña, they only do it 32% of the time. (The other end of that: Chicago’s Gavin Sheets, who has seen similar opportunities, in that the expectation is a 36% advance rate, but has actually seen runners go 43% of the time on him.)

Acuña and Tampa Bay’s Jose Siri are the only two outfielders to accumulate at least a full run’s extra value in runners holding (+5, in Acuña’s case) than in allowing advances (-4). Going back to his 2018 debut, he’s tied for second-best in getting runners to hold (+23), despite missing nearly an entire year due to his 2021 knee injury. That, for all the great throws and incredible assists, tells you just as much about how opponents feel about Acuña’s arm. While his ability to turn batted balls into outs is somewhat below-average (-4 runs this year, per Statcast), the arm is so good that it entirely makes up the difference.

Take a look at that same play against the Orioles again, but this time side-by-side with a nearly-identical chance in a late-May Royals/Cardinals game. Right fielder MJ Melendez was exactly the same distance from home as Acuña was, 269 feet. He’s got a strong arm (92.4 mph this year), though not quite as strong, and the two baserunners (Henderson and Tommy Edman) have extremely similar above-average speed.

Henderson wouldn’t dare. Edman scored easily.

Acuña is hardly the only great arm in the outfield, of course. Who else rates well in Statcast arm measures? At the moment, there are four outfielders worth at least +4 throwing runs at the top of the 2023 leaderboard. One is Acuña. The other three are …

Adolis García, Rangers (+5)

If Acuña rates the best at preventing runners from trying it at all, then it’s García who currently sits atop the overall leaderboard at +5 throwing runs, just ahead of a trio (including Acuña) tied at +4. For García, that breaks down into +6 for actually throwing runners out, the best in baseball, +3 for preventing them from even bothering, and -4 when they’ve managed to take the extra base against him.

It was, we can confirm, not terribly difficult to find a highlight of García making some baserunner’s life miserable -- like when he threw out Vladimir Guerrero Jr. by so much that catcher Jonah Heim had to be careful not to put down the tag too early.

But the most entertaining ones are when the runner has hardly even rounded third base and you just know it’s going to end horribly, as in this example, when Baltimore broadcasters start groaning before García has even uncorked the throw.

Over his three years with Texas, García rates second overall in throwing runs (+10) behind Michael A. Taylor, but first in runs from actually throwing runners out (+15), ahead of Hunter Renfroe (+14). This year, when runners attempt to go, no one makes them regret it more often.

Lane Thomas, Nationals (+4)

Briefly a Minor League teammate of García (and Randy Arozarena) in the St. Louis system, Thomas is in the midst of a breakout season for Washington (.844 OPS) and might find himself being a sought-after piece at the Trade Deadline. Like Acuña, he hasn’t been terribly strong in collecting batted balls (-3), but his arm has been so good (+4) that it makes up the deficit and then some.

Given his strong arm -- the former high school pitcher is just a tick behind Garcia at 92.9 mph, and he’s touched 101.6 mph this year -- this shouldn’t be surprising. But he’s also responsible for one of the highest-rated assists of the season, given just how far he had to go to get to this ball hit by Nick Castellanos, who was then thrown out trying to stretch it into a double.

Castellanos, perhaps, isn't considered a burner on the bases. But Arizona's Corbin Carroll absolutely is:

"He’s a very smart defender out there," Washington pitcher Patrick Corbin told MASN earlier this season about Thomas. "Seems to always hit the cutoff. Makes accurate throws." He then later added just about the best compliment an outfielder can receive from one of his pitchers. “I was joking with him: I’ll just give up singles to him all day, and hopefully they try to stretch it to a double. He’s been doing it all season.”

Joey Wiemer, Brewers (+4)

Perhaps the most interesting name on this list, simply because the rookie Wiemer doesn’t have quite the cannon that the three names above him do. Unlike Acuña (99th percentile in arm strength), García (96th), and Thomas (95th), Wiemer’s 88.2 mph average puts him in the solid-yet-not-elite 75th percentile -- or comfortably above average without being a showstopper.

Unlike the other names here, there’s not one aspect where Wiemer has excelled so much as it is that he’s been above-average at throwing runners out and preventing them from trying to advance.

So, while it’s fun to watch him get the out ..

… it’s also entertaining to watch runners not take the risk either.

Wiemer is doing this while also playing something of a new position. Through the All-Star break, Wiemer had started 78 games in center, after having started just 44 games there as a Milwaukee Minor Leaguer. (He’d primarily played right field.) But he’s been so good there that through the All-Star break, he rated as the second-best defender in the game this season, adding +6 runs with his glove and +4 more with his arm.