Ground Balls Are Changing.

Major league batters are generally shifting towards a fly ball approach. The idea is to hit more balls in the air. Not necessarily fly balls, in fact there are those who wish to only hit line drives. When I say in the air, I mean ‘not on the ground.’ You want the ball to leave the infield before it bounces, ideally. Preferably this happens at a very high speed.

Duh, no kidding, right? Well, yeah. Obviously hitting the ball out of the infield is the goal for just about everyone. The goal isn’t the key, we’re talking about the approach used to actualize the goal.

There are two big schools of thought on this issue.

The ‘old school’ approach which stresses a level bat plane. Not level to the ground, level to the pitch. The idea here is to increase your chances at making solid contact, and allowing the hard contact to find a hole in the defense.

This approach makes sense. You hit the ball hardest when your bat is perfectly in line with the pitch. The ball and the bat meet head on and generate the most energetic collision that is possible given pitch speed, bat speed, etc. When your bat is in plane with the pitch, you hit the ball as hard as you possibly can. If you continually hit the ball this hard, you’ll probably get a few hits. And every so often you’ll be just a little under the ball, and hit a homer. And sometimes you’ll be just a little over it and hit a grounder.

The approach makes sense. You can see how the pieces fit together and the logic behind it.

The ‘new school’ approach stresses going out to meet the ball in front of the plate. It accepts that the bat path shouldn’t be a straight line, but rather more of a curve, like a swinging pendulum. It starts high, goes low, and then comes back up. You want to hit the ball when the swing path is going upwards, so you’re attacking the ball from the bottom. It takes time to get to that point in the swing, so in order to maximize the effect you attack pitches further in front of home plate, guaranteeing that you are hitting balls during the ideal part of your swing.

This ‘new school’ approach is getting more and more common, and I apologize if I am oversimplifying it. There are many reasons a player may be drawn to this approach, ranging from pitch selection to cuing. There are also reasons a player may not benefit from this approach, ranging from bat mechanics to cuing. Cuing is actually a really big deal.

Cuing refers to which words make you remember how to perform properly, which in turn depend upon how you internalize and understand the world around you. People with different understandings may find different cues useful and others confusing and vice versa.

Regardless of all of these schools of thought, batters appear to be hitting fewer ground balls. So, that’s great, right? Well, um, maybe not. The nature of ground balls are also changing somewhat dramatically. Look at this gif comparing the 2015 and 2017 seasons. The colors are wordy to explain, but simple to understand.  Each row is a launch angle (2 degrees). For each row the highest frequency exit velocity (separated into 2 mph chunks) is dark green, and all of the other squares are based upon their percentile compared to that most frequent exit velocity.

In order words, if the largest square contains 400, then one that contains 200 would be 50% and one that contains 300 would be 75%. Makes sense, right? Pretty simple. Just remember that this is done row by row, so each launch angle is shaded independently.

Notice how the low launch angle balls are losing velocity and high launch angle balls are gaining. This is what you would expect from players trying to hit more fly balls. Trying to hit more fly balls doesn’t necessarily mean you hit fewer ground balls, rather your ground balls are significantly weaker. This is because the further the launch angle is from your swing plane, the lower the exit velocity.

Low launch angle ground balls are becoming less frequent. Amongst batters who played in each of 2015, 2016, and 2017, balls hit below 0 degrees have gone from 35.7% in 2015, to 34.7% in 2016 to 31.6% in 2017. A steady drop year to year. The exit velocities are even more staggering: 83.7 mph in 2015, 85.7 mph in 2016, and 78.4 mph in 2017.

The frequency of these weak batted balls is going down, but the exit velocity is going down even faster, and there is no reason to believe this trend will reverse course. The change from 2016 to 2017 was dramatic, to say the least, and I am not sure another change this dramatic could occur in 2018. However, maybe we will see only 30% of balls hit below 0 degrees. Perhaps these balls will have an EV of only 77 mph. I don’t know where these numbers might land, but the trend is clear.

What does this mean going forward? Well, if ground balls continue to lose value through a combination of weaker hits and better shifts then we may have to rethink where ground balls fit in the spectrum of batted balls. Prior to Statcast it was difficult to study and analyze balls hit between 0 and 15 degrees. You could call them line drives and quote line drive stats. There is far more you can learn from these balls, though.

Developing the knack for identifying and capitalizing on skill sets that promote these intermediate launch angles may become one of the most important skills for fantasy players. There are big name bats that take advantage of these trajectories: Freddie Freeman, Joey Votto, Corey Seager, Andrew McCutchen (the good version). There have also been lesser names who became stars after taking advantage of these trajectories. Guys like Justin Turner and Chris Taylor.

Rather than only looking at ground ball versus fly ball stats, you may want to start looking into these intermediate launch angles.