FOLLOWING THE RULES

MLB has tested the ABS challenge system for years, just as it did for every previous rule change

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Spring training this year has given fans a reason to think about the strike zone in more detail than ever before. The experimental use of the automated ball-strike challenge system has led to a lot of fans wondering why the strike zone being used by robot umpires doesn't match the one they've seen in the rule book.

This is the part of baseball that has usually bubbled beneath the surface. You might know what should be a strike and what should be a ball. But if asked to define the two, things get complicated quickly.

If you have ever used the term "hollow beneath the kneecap," you've definitely read the official MLB rule book. If you've ever given thought to where the midpoint between the top of the shoulders and the top of the uniform pants truly resides, you've likely umpired games at some point.

But as MLB has edged closer and closer to bringing the ABS challenge system to regular season games, the success of that system has depended on putting that rulebook definition back on the bookshelf.

Whenever MLB has tried to match the rulebook definition of the strike zone in its many minor league, Arizona Fall League and Atlantic League experiments, it has done nothing but frustrate batters, pitchers, umpires and fans.

By being strict to the rules, the ABS zone seemed to be out of whack.

Only by being willing to be unconventional has MLB gotten to the point where the robo umps can call what we perceive as the conventional strike zone.

The strike zone is exceptionally complicated.

It has moved around from era to era, but anyone who watches a lot of baseball gets acclimated to the "normal" zone pretty quickly.

Now, that version of "normal" will change.

In the 1945 MLB rule book, the strike zone was defined as being "not lower than the batsman's knees, nor higher than his shoulder." Imagine a modern day batter getting called out on a fastball at collarbone height.