MLB is testing a check swing challenge system in the Arizona Fall League

It’s interesting and cool… but needs some work.

One thing that’s been endlessly debated among baseball people: Exactly what is a “check swing”?

In some games in the Arizona Fall League, MLB is now testing a challenge system that aims to specifically define that.

This article by Sam Dykstra at MLB.com explains how it works:

Using the same Hawk-Eye technology as the Automated Ball-Strike Challenge system already in place in the Arizona Fall League, the Check Swing Challenge is being used on a limited basis in a proof-of-concept stage at Salt River Field.

Teams will be able to challenge an on-field check-swing call to see if the swing crossed a 45-degree threshold from home plate.

So that’s the simple version. Here are a couple of examples of how it worked in a recent game at SRF:

Here’s the thing. I always thought a “check swing” meant that either the hitter “broke his wrists” (not literally, of course) or that the bat crossed the plate. In the examples shown above, the bat goes well across the plate.

If this is how the league wants to define a “check swing,” that’s fine, as there never has been an official definition. As noted in Dykstra’s article, these challenges, like the ball/strike challenge system, must be called immediately after the event by the batter, pitcher or catcher. Similarly, video is shown right away and the entire process takes only a few seconds. Each team gets two of these per game, and if they use them up by the eighth inning, they get another one for the ninth.

This is a really interesting concept and an attempt to specifically define something that’s never been so. Obviously, this is a work in progress and as of now, is being tested only at SRF.

Here’s a bit more in an explainer from Baseball America:

I like this idea and hope they can make it work. Of course, I’d like to see the challenge system for balls and strikes brought to MLB as soon as possible.