Those three stats (K%, BB%, BB/K) are the bulk of what is used to determine a player’s plate discipline, but there are actually quite a few more advanced stats that can be used get a much deeper look into a player’s approach at the plate. It’s really not necessary to get very in-depth with these stats, but a simple description and league context is really all you need to be able to apply them.
It waters down bad play of many and you are more willing to use players despite their weakness as a player are one-sided arguments made to favor BA. Doesn’t batting average reward hits and dismiss players that walk. And since when is drawing walks considered bad play, it’s a basic fundamental taught throughout the minors and is a sign of a patient hitter. The weak hitters are the ones that can’t draw walks, and those players can be seen hacking away with a sub-par batting average when then get close to or in their 30’s.
When you are stronger you will be able to hit through the baseball without the bat slowing down too much at contact. If you have ever watched the Little League World Series and watched slow motion replays of hitters hitting a homerun you will notice that the bat almost stops at contact because they are not strong enough to power through the velocity of the pitch.
Now that we’ve covered slash lines, plate discipline, and batted ball data, that about does it for the hitting side of advanced baseball stats, but before I wrap up, I need to mention one important thing. All of the statistics that I used were from players who had a qualifying season (3.1 plate appearances per team game which is roughly 500 PA). The pre-mentioned stats are most effectively used when you have a good sample size of data to work with, and you should watch out for stats that are skewed by small sample sizes. Make sure that when you are evaluating a player’s skill set, they have accumulated enough plate appearances (usually you want to aim for a minimum of 100) to make the data you’re working with relevant.
Exactly how humans are able to estimate the expected position of a quickly moving ball is unknown. Obviously, this remarkable skill is learned through long practice. Eye-brain-body coordination is acquired only by going through the motions over and over; even so, the batter misses most of the time. Getting a hit three times out of ten at bat is considered an excellent average. It's interesting that George Schaller and other ethologists have observed that lions and cheetahs are also successful only about a third of the time in capturing their prey.
While batting average is a useful tool for measuring a player's ability at the plate, it isn't all-encompassing. For instance, batting average doesn't take into account the number of times a batter reaches base via walks or hit-by-pitches. And it doesn't take into account hit type (with a double, triple or home run being more valuable than a single).