© Jerome Miron/Imagn
What is exactly is check swing? Well, the Major League Baseball rulebook does not actually contain an official definition for a checked swing. But it defines a swing as “an attempt to strike at the ball.” Seems vague, right? Well Minor League Baseball is set to trial an automated challenge system in hopes of clearing things up.
There’s just one big problem. We still don’t know what a check swing is, and the automated system looks set to redefine what we all thought constituted a swing. Currently, umpires typically rule that a player swung if their bat passes a 90-degree angle relative to the player or, similarly, the front plane of home plate. But the automated system, which went into use on Tuesday in the Single-A Florida State League, has a far different view of things.
Major League Baseball will begin experimenting with using bat-tracking technology to call check swings starting tonight in the Single-A Florida State League.
More details: https://t.co/rzg2fd3A7c pic.twitter.com/aO9BIVSHpl
— Minor League Baseball (@MiLB) May 20, 2025
New Technology Places Threshold For Check Swing At 45 Degree Angle Past Plate
“Using the same Hawk-Eye system as ABS, a swing will be called when the head of the bat moves ahead of its knob by more than 45 degrees,” an explanation of the system states. “Anything less than that will be considered a non-swing. For a clearer visual, the baselines both extend at 45-degree angles from home to first and third. Each club will have one Check Swing Challenge per game and will retain the challenge if it is successful.”
That’s uh, a much different interpretation of a check swing than we all thought, right? Putting the threshold for a check swing a 45 degrees gives batters a lot of leeway that they did not previously have, and fans were a little puzzled.
“Where did MLB come up with this 45° rule? This is definitely not how the rule is enforced today,” one fan on X asked.
“I recently told someone this had to be in the pipeline. That being said, 45 degrees past the front of the plate is crazy. It should be breaking 0 degrees at the front of the plate,” said another.
Ultimately, I’m fully on board with check-swing technology. It seems like an extremely easy way to sort out one of the most controversial plays in the game. But we all agree that 45 degrees is a ridiculous threshold, right?