Exit velocity isn’t the whole story

Among the various new metrics introduced via Statcast, exit velocity has become the most ubiquitous. It makes sense too. We’re now able to measure exactly how hard a batter is hitting a ball, something so visceral and easy to understand that it’s hard to believe we didn’t have this information earlier. A few days ago, Marc from USS Mariner had some interesting comments about early exit velocity returns for a few Mariners. In that article, he revealed a common pitfall that can hinder our observations; exit velocity only tells half the story.

Of course, hitting the ball harder is always a better outcome than hitting the ball weakly, but the distribution of those balls in play matters too. This is where launch angle enters the conversation. Two batted balls with an exit velocity of 100 mph will have very different outcomes if their launch angles are vastly different. This make intuitive sense but even I’ve fallen into the trap of just looking at exit velocity in a vacuum.

We’re getting to the point in the season where exit velocity and launch angle are becoming statistically reliable (around 30 balls in play). So I went to Baseball Savant to pull the relevant data to see if we can glean anything interesting. Below you’ll see a table with each batter’s average exit velocity, the number of balls in play hit with an exit velocity greater than 98 mph, and the average launch angle on those hard hit balls. (I chose 98 mph as the cut off because that’s the point at which barrels—a new Statcast metric—are calculated.)

Taylor Motter leads the pack by a wide margin. I’m cheating a little bit because he only has 16 tracked balls in play this season, but that also means that more than 60% of his balls in play have been hit harder than 98 mph! It isn’t surprising to see Cruz and Cano atop the leaderboard either. I’m more interested in the group of players sitting around 87 mph (incidentally, league average exit velocity is around 87-88 mph).

Leonys Martin in particular is an odd case. If you read the USS Mariner post I linked to above, you’ll probably already be familiar with Martin’s struggles. His average exit velocity isn’t the problem, it’s the distribution of those balls in play when he squares one up. For those balls hit with an exit velocity greater than 98 mph, his average launch angle is -5.3. He’s hitting some sharp ground balls but that’s certainly not the most ideal outcome for a hard hit ball.

If a line drive or fly ball is the most ideal outcome for a hard hit ball, let’s break down the data even further to see who’s getting those ideal outcomes. Below you’ll see another table with each batter’s average exit velocity for the different batted ball types and the number of hard hit balls in play for each type as well.

Mitch Haniger is the poster child for maximizing his batted ball outcomes. His overall average exit velocity is a bit below league average but he really shines when he’s hitting the ball in the air. He’s tied for second on the team with eight balls in play hit in the air with an exit velocity greater than 98 mph. He might have a few more weakly hit ground balls and lazy fly balls mixed into his batted ball distribution than we’d want to see, but when he gets a hold of one, he does some damage.

Danny Valencia also comes out looking better than his raw offensive numbers might indicate. His average exit velocity on his fly balls and line drives is tied for third highest on the team and his batted ball distribution skews towards those types of hits. He’s gotten extremely unlucky on those hard hit balls in the air too. Four of the six hard hit line drives have been caught and he has just a single and a double to show for the other two.

It’s probably too early to overreact to Valencia’s struggles at the plate. The slow starts by Cruz, Cano, and Seager will soon be in the rear view mirror. But Leonys Martin needs to figure out his swing. He was working on different mechanics during spring training and the quickly changed back to his old mechanics about a week into the season. You have to wonder what so much tinkering has done to his swing.