For baseball professionals and amateurs across the globe, the dream is to reach the major leagues, and every single year, there are dreams fulfilled that belong to players I’ve never heard of before. Like most baseball writers, I know something about most players, but there are a lot of players, and I have only so many brains. Some months ago I didn’t know a thing about Scott Rice. Scott Rice is the major-league leader in appearances, for pitchers. Usually, the players I don’t know are relievers, but every so often they’re utility infielders or versatile outfielders. Generally, they tend to be relatively unremarkable. I’m supposed to know the guys with big talent. Generally, I don’t expect the players I don’t know to go on to rank among the league’s best at something.

It took me a little while to recognize the name “Juan Lagares.” I’d never heard of Lagares when he started getting playing time with the Mets, and I was left unimpressed by a glance at his statistical track record. But, at the plate, Lagares has gotten better, and at the plate isn’t where Lagares is at his most interesting. See, Lagares has been his most remarkable defensively. Just Wednesday, he robbed the Braves of at least one run with a diving catch at a sinking liner. And while Lagares has demonstrated his ability to move around the outfield, range hasn’t even been his strength. His range has been good, but his arm has been outstanding. Juan Lagares’ arm has put him on a leaderboard.

One thing to know about Lagares: he hasn’t been a full-time player, not all year long. He’s right around 700 defensive innings or so. Another thing to know about Lagares: at present, he ranks second in baseball in outfield assists. And we can do better than just looking at outfield assists.

Included in UZR is an arm component, known as “ARM”. It takes into consideration not just throws and kills, but also baserunners prevented from moving up. You know, stuff that arms do. Lagares has an ARM rating of +11.5 runs, easily tops in baseball. And we can expand the picture beyond just 2013.

We have this data going back to 2002, so let’s look at that whole window, splitting seasons and setting a minimum of 500 innings in the outfield. Let’s take a look at the best ARM seasons, giving everyone a consistent denominator of 1,000 innings. A table of the top ten:

I, also, had forgotten that Miguel Cabrera was an outfielder. But this is about the name at the top of the table, not the bottom. At least so far, Juan Lagares’ arm has been a legitimate weapon — arguably the most effective outfield arm in at least 12 years. Of course, we need to give him more time, and of course, we expect all extreme performances to regress, but if you’re looking for the thing that makes Juan Lagares most notable, here you go. He’s shut down the running game better than anyone else.

Here’s a little footage of Lagares striking down Jason Heyward:

Here’s a little footage of Lagares striking down Heyward again, the next day:

So what is it that makes Lagares so good? When you imagine a great arm from the outfield, you imagine a great arm from the outfield — an arm that’s incredibly strong, and incredibly accurate. Something like vintage Ichiro, or Francoeur, or even Yasiel Puig. Lagares doesn’t have a weak arm, and his throws are typically accurate, but this isn’t something people talked about as Lagares climbed the organizational ladder. Lagares actually started as an infielder. From a report from 2010:

He has the speed to cover plenty of ground and a solid average throwing arm.

From Kevin Goldstein in 2012:

Originally an infielder, he’s a solid-average runner who has improved in the outfield, and his arm is solid.

Lagares’ success might have a lot to do with his background as a shortstop. He hasn’t actually played short at all since 2009, and he hasn’t played it regularly since 2008, but you can see the shortstop instincts in the throw below:

More substantively, there’s evidence that Lagares has a particular way of approaching batted balls hit in his direction. A few weeks ago his arm got him some coverage in the Wall Street Journal. Interesting theories and explanations were advanced.

Mets players and coaches say that Lagares has the ability to run in to retrieve ground-ball and line-drive singles faster and more aggressively than any player they have seen. As a result, when Lagares picks up the ball, he is physically closer to home plate than other outfielders, giving him an advantage when it is time to make a throw.

[…]

“He’s closer to second base than anybody I’ve ever played with,” catcher John Buck said. “You get a jump that good, you have to be anticipating, your wheels have to be turning. That’s something I’ve never seen.”

[…]

Most outfielders, Buck said, have to slow down while charging in to field ground-ball singles to ensure that they don’t skip behind them. That’s because they aren’t used to handling the tricky hops and bounces.

Lagares ordinarily plays more shallow than most center fielders. He has a good first step and a lot of confidence in his own ability to track fly balls over his head. He runs the right routes, and because of his speed and trust in his ability to retrieve a ball and throw it on the move, he cuts down the distance a thrown ball spends in the air. Though Lagares doesn’t have baseball’s strongest arm, so much of his work in the outfield optimizes things, allowing him to make the most of what he has. Baserunners just have less time to run.

Here’s a play that Buck talked about, against the Padres:

The throw didn’t make it to the catcher on the fly, but it arrived where it needed to, and Lagares initially approached the ball aggressively and threw from unusually close to second base. Here’s an overhead view of a different play, where Lagares picked up another assist. For an idea of how shallow Lagares sometimes lines up:

His subsequent position when he threw:

That play itself was a confusing one, where the baserunners believed that Lagares caught the ball instead of trapping it, but you get a sense of what Lagares does in center, and how close to the infield he can end up.

In a general sense, Lagares is a good reminder that there are different ways to be defensively outstanding. Some players are blessed with nearly unparalleled lateral range or instincts. Some players have impossibly strong and accurate arms. Andrelton Simmons is an amazing shortstop because of his arm, and because of his hands. Brendan Ryan is an amazing shortstop because of his instincts and positioning. Jeff Francoeur can control the running game with his arm strength. Juan Lagares can control the running game with his footspeed, aggressiveness, and arm accuracy. And teams are going to notice, if they haven’t already. Teams are going to take fewer chances against Lagares going forward. He’s going to be a known factor.

It’s probably not a flash in the pan. A year ago in the minors, Lagares recorded 17 assists in 126 games. This year in the minors, he recorded four in 17. There’s no need to test Juan Lagares anymore — his ability should be understood. Even without a true cannon, Lagares does so many other things well that it’s basically the same idea. Lagares can be death to flying things and to running things. There’s every reason to challenge Juan Lagares when he’s standing at the plate. When he’s pursuing a ball in the field, though, one should be content with what one can get.