There’s been a lot of talk about Yandy Diaz‘s exit velocity so far this season and how it proves he’s ready for the big leagues, despite his low batting average.
But there’s also been a lot of backlash to the increased use of exit velocity from the anti-analytics crowd. So before diving into the stats I think it would be helpful to address this issue.
Of all the advanced stats that exist in baseball, exit velocity should be the least controversial. Let me explain…
Remember in little league when you hit a ball hard, but it went right at a field and your coach said something along the lines of “Great hit! That’ll drop in there next time.”
Or have you ever heard a manager talk about a slumping player in a press conference and say something along the lines of “He’s hitting the ball well, they’re just not falling for him right now.”
Well, that’s exit velocity.
Baseball players have known since the 1800s that if you consistently hit the ball hard, you’ll get hits. Sometimes you’ll experience a spell of bad luck when these hard hit balls end up going right to the fielders, but in the long run if you keep hitting the ball hard you’ll be fine.
So the increased use of the term “exit velocity” isn’t even remotely due to a new concept entering the game. We just finally have numbers to support what we’ve always known. Now when a coach claims a player is hitting the ball well and experiencing bad luck, he can actually support that with facts.
And that’s where we stand with Yandy Diaz.
Through Saturday, Diaz leads the Indians with an average exit velocity of 95 mph—an almost impossibly high rate. According to this chart shared by MLB.com’s Darren Willman in 2015, a 95 mph exit velocity should typically lead to a batting average well above .300
— Daren Willman (@darenw) October 24, 2015
For good reason, a lot of people (myself included) have been pointing to Yandy’s exit velocity as proof that he is ready for the big leagues. And that’s true to a certain point.
An average exit velocity of 95 mph is impressive—you don’t just accidentally crush the ball like that in your first couple weeks in the majors. But exit velocity is only one component to a good hit.
The other piece of the equation is launch angle—another term that’s getting some backlash from the anti-analytics crowd. But just like with exit velocity, we’re just putting a number on something we’ve been talking about for the past century.
Ground balls and fly balls sometimes yield good results, but only when they’re hit hard enough that fielders can’t get there. And line drives are always good, but sometimes you have bad luck and hit it right at someone. Agreed? Good, that means you’re on board with launch angles.
So here’s the issue with Diaz: he’s crushing the ball, but almost exclusively hitting ground balls (in other words, very low launch angles).
Ground balls aren’t entirely bad, but since there has been such an emphasis placed on infield defense in recent years and shift rates continue to rise, more and more players are intentionally trying to hit the ball to the outfield. This leads to more easy fly balls, but it also leads to more home runs and line drives into the gaps. In terms of old school baseball terms, remember hearing about certain guys who were “doubles hitters?” These were the launch angle superstars of the past—guys who were consistently hitting the ball to the outfield and finding the gaps.
Five Thirty Eight shared this graphic showing the relationship between launch angle and exit velocity—I’ve added in a note to show where Diaz’s average hit has fallen this year.
As you can see from the chart, despite his extremely high exit velocity, his success rate falls into just an average range. This chart is evaluating performance based on LWTS—I won’t get into the specifics, but basically it’s how many runs you’re generating, therefor extra base hits are viewed as far more valuable than singles (hence the dark orange in the HR area).
Diaz’s hard hit ground balls are great for producing singles—and in the long run he should have a high batting average with his approach. But he will generate very, very few extra base hits with a launch angle of zero, no matter how hard he hits the ball.
The image below, from MLB’s Baseball Savant, shows the outcome of all 95 mph/0 degree balls hit from the 2015 and 2016 seasons. They generated an impressive batting average (.357) but only four percent of all hits went for extra bases.
Obviously we’ll all sign up for a .357 hitter, regardless of how many extra base hits he gets. But the issue with Diaz’s launch angle is there’s no room for error. If his exit velocity falls to 90 mph (a more realistic long-term average) but his launch angle stays at zero, that equates to a .266 batting average with zero extra base hits—and that is clearly not the profile of a major league hitter.
So what do we make of Diaz’s performance? Is his exit velocity still exciting even though it’s accompanied by a poor launch angle?
It’s really hard to answer those questions definitively because these stats have only been tracked for two seasons. But anecdotally, it seems to be accepted that it is easier to adjust your launch angle than improve your exit velocity. Diaz already has the skills to hit the ball hard, now he just needs to tweak his approach to generate more line drives into the outfield which will produce even more exciting results.