@Rush51
Due to gravity the ball is not crossing the plate level, but on a downward angle.
Balls with a moderate launch angle have been proven to produce better results.
Around 10-20 degree angle have proven best.
Ground balls simply get fielded easier, do not produce homers, and rely too much on speed.
At that angle they produce more line drives, carry into the gaps, and will produce more homers.
If you graph it out as Y=a*x(squared) you will see it better. The hitters want enough of an upper swing before gravity pulls it down while not popping it up.
Over the last several years batters have been taught this and the batters have gotten much better at getting it right.
This will also produce the proper amount of backspin to allow the ball not to drag as much and carry further.
This is why hard-hit balls travel further than top-spin grounders do.
When you look at the human biomechanics it is easier to understand why this works the way it does.
However, when people say 'uppercut' they get it somewhat confused with, say, a golfswing. It is not that exaggerated.
You want enough of an uppercut to avoid popups, etc. You want a 'controlled' upward path with the bat and not an exaggerated uppercut.
It has taken me a long time to come around to admitting that this is better in today's game.
With the advent of computers to study the biomechanics, the models to study the expected runs produced, etc. it has changed the game. Leg drive, hip rotation, hand delivery through the swing, torso torque, etc.
I still like BA and BB, etc. Because I like the hitter to get on base more. But I also realize that the hitters today are NOT contact hitters like in years before. So, the small ball does not work well enough to produce runs.
But it really is better for the team when you have folks that have been shown to 'produce' more runs in the long run and not just get on base and hope the next guy can do the same.
The issue is that Mike Trout was pretty much a natural at this from the start and was far ahead of the way the game developed.
It is not about swinging as hard as you can and either hoping for a homer or striking out --- like some of the 'power' hitters from years back.
Now it is all about controlled launch angles to drive the ball.
The last thing I would add is that because of the length of the baseball season, the large amount of games, and the huge numbers of in-game scenarios baseball has been the ideal sport for analytics to play out and actually work. For example, in a 16-17 game NFL season they do not have enough time to average out over a year to have a net benefit as much as in MLB.
