A Brief Tangent on Arm Strength

Ceddanne Rafaela has a weak arm. He additionally has a powerful arm.

That is an evaluation I’ve wished to do for some time. It’s not that vital or sophisticated, and most of it’s pretty apparent. Nevertheless it will get at one thing that comes up every now and then within the varied locations baseball is mentioned on-line. The dialog tends to start out like this: Staff A ought to signal Participant X and transfer him to a brand new place. Inevitably, one of many first questions requested about such a plan is whether or not Participant X has the arm energy to play that new place.

The quantity that will get cited to “yay” or “nay” such a follow-up is arm energy, in miles per hour. However ask any baseball fan to sit down with this for a second, they usually’ll elevate a priority. Arm energy, to a point, is a operate of place. A 3rd baseman has an extended throw to make than a second baseman. A proper fielder has an extended throw to make than a left fielder. This implies gamers with higher arms are inclined to play these positions, as we will see on this plot:

It additionally means the official arm energy figures reported by Baseball Savant aren’t fairly transferable between positions. We will’t say whether or not Participant X has the arm energy for a given place if he’s by no means performed there earlier than.

That brings us to Rafaela. Most followers consider him because the next-best middle fielder within the majors after Pete Crow-Armstrong. However Rafaela additionally occurred to play 24 video games at second base final yr. His printed arm energy at second base in 2025 was 78.5 mph. In middle subject, nevertheless, his printed arm energy was 93.4 mph. Since 2021, that’s the most important hole for a fielder between two positions (excluding first base):

Wanting on the plot, if we assumed Rafaela’s printed arm energy at second base can be his arm energy in middle subject, he would have one of many three weakest arms in middle final yr. As a substitute, he wound up having one of many strongest. That’s as a result of that is the kind of throw that will get an out at second base:



Whereas that is usually what it takes to get an out from middle subject:

It’s price noting the methodology behind the arm energy figures you see on Baseball Savant. Mainly, it’s the typical of a participant’s strongest throws. From the Baseball Savant arm energy leaderboard:

Because the calls for of every place grouping are completely different, the averages and qualifiers are completely different as properly.– 1B: common of prime 1% of throws (minimal 100 throws to qualify);– 2B/SS/3B: common of prime 5% of throws (minimal 75 throws to qualify);– OF: common of prime 10% of throws (minimal 50 throws to qualify)

So, how a lot arm energy may we count on a participant to achieve or lose with a place change? I discovered the entire gamers with the minimal variety of throws at a number of positions in a season since 2021. I then took their arm energy at every place and averaged the variations. It’s about what you’d count on. Gamers throw more durable after they’re in proper subject than they do at first base: 


Whereas performing this evaluation, I discovered that Tom Tango had accomplished a extra complete piece on these positional equivalencies, wanting particularly at gamers who moved between any two positions. Utilizing his technique provides us this good grid:

As an illustration, a fielder transferring from second base to middle subject provides about 6.5 mph on common to their arm energy determine. Rafaela gained practically double that, going from a roughly common throwing second baseman to one of many hardest throwing outfielders within the league. However how a lot is all that arm energy price?

By way of worth, arm energy is the lesser of the fielding abilities in comparison with vary. There are merely fewer alternatives to utilize a powerful arm. Baseball Savant solely publishes arm worth elements for outfielders, the place arm and vary are simpler to separate than they’re for infielders. Arm worth is derived via a sequence of estimates and charges, evaluating how usually a baserunner ought to try to advance on a fielder with how usually they really do (and the way usually they achieve this safely). That is accomplished utilizing a distance-time mannequin, which considers the velocity of the runner, the arm of the fielder, and the space every are from their goal.

In different phrases, arm worth isn’t nearly pure energy. Stopping runners from advancing requires quite a lot of different abilities, like attending to the ball, fielding it cleanly, and making an correct throw. And even an important throw relies on one other fielder receiving the ball and making use of the tag. Plus, a runner’s choice to advance is partially primarily based on the sport state and different nuances particular to a play. There are various causes a powerful arm doesn’t at all times equal a priceless arm, and vice versa.

This additionally implies that every outfield place has a distinct baseline arm worth:

Arm energy appears to be most impactful for proper fielders. That’s attention-grabbing, although it’s additionally pretty intuitive. Proper fielders are sometimes requested to make very lengthy throws, and may get dinged for permitting runners to advance. These with sturdy arms are each extra more likely to throw runners out and to persuade runners to remain in place.

I additionally marvel if there’s a repute benefit. Balls hit to left subject, as an example, permit the runner to learn and react to the play in entrance of them, whereas balls hit to proper subject drive the runner to check with the scouting report. I’m positive many runners really feel uneasy after they can’t see Addison Barger:

Middle subject arm worth is the least attentive to arm energy. There’s simply not quite a bit even the strongest arm can do from 400 ft away. A middle fielder with a priceless arm is a middle fielder who takes a very good path to the ball and cuts it off clear, fairly than one who racks up assists.

Rafaela occurs to have all these abilities. He has each great vary and a powerful arm. He completed 2025 with two runs above common from his arm, seventh amongst middle fielders and within the prime 15% amongst outfielders. That’s not quite a bit, however hey, it isn’t unhealthy for a soft-tossing second baseman.