It has been well documented that there have been more home runs this seasons compared to the past few years. It is particularly interesting because guys we may not necessarily associate with home runs have received a large bump, while the higher end power hitters haven’t had any noticeable increase. Daniel Murphy, Asdrubal Cabrera, Jose Altuve, and Brad Miller have hit 20-30 homers this year, guys like Robinson Cano and Brian Dozier are getting huge boosts to already good power production, and others like Anthony Rizzo and Manny Machado don’t seem to have any significant change at all.
There are a ton of variables involved here, pretty much everything under the sun could be brought up as an explanation. You could point to the individuals and claim some players happened to have bad seasons last year, or good seasons this year. Maybe certain guys have corrected flaws in their swing or pitch selection.
Even when accounting for all of that, we’re seeing a real change in production this season, something that goes beyond small blips or statistical noise. Many researchers have shown, using various methods, that exit velocity has gone up this season. I’m sure you’ve already read the arguments, and if you haven’t here is a link. I’m more interested in why certain players may be benefiting while others are not. So, yes, on the aggregate, we know exit velocity is up, but how is it affecting batted ball distance, and are the changes helping some sorts of players more than others?
Below you’ll see three charts. In each case, the x axis shows exit velocity, and the y axis shows vertical launch angle. I’ve narrowed it down to only balls hit over 80 mph and between 15 and 45 degrees. We’re talking about just the upper end of line drives spectrum plus fly balls. Ground balls and pop ups are eliminated. Each chart is color coded based upon average batted distance, using the Statcast distance, where blue represents shorter distances, and orange/brown represents longer distances. The first chart shows 2015, the second shows 2016, and the third shows the difference between the two, where blue represents balls hit further in 2015 and orange/brown are those hit further in 2016.
You may need to open the link in a new tab to switch between charts, I highly suggest doing so.
The 2015 and 2016 charts look very similar. A little bit of noise in the data, perhaps. Take a look at the difference chart, though. I don’t know about you, but I see a pattern here. I’ve highlighted the pattern using two groups, which you can toggle on and off. In the lower angles, between 15 and 23 degrees or so, 2015 batted balls going further, and in the upper angles, between 27 and 43 or so, 2016 balls going further.
I went through and averaged the differences using only batted angle on balls hit between 80 and 105mph, and you can see the results in the chart below. The story checks out, between 15 and 23 degrees, for the most part (all excluding 21 degree launch angle for whatever reason) the balls in 2015 traveled farther. Not by much, but by some. About 2 feet or so. Between 27 and 44 degrees, the ball has traveled farther in 2016. A lot farther, actually, between 3 and 11 feet. About 7 feet on average between 33 and 39 degrees.
|Angle||2015 feet||2016 feet||Average Difference|
This is interesting, but it raises more questions than it answers. If the ball is flying farther on higher batted ball angles in 2016 and shorter on lower angles, then you would think that batters who tend to hit the ball on these higher trajectories are more likely to hit homer runs this season, compared to last season. Although, looking at some of the names from before, the guys who are seeing a surge in home runs, these guys look like line drive hitters to me. Perhaps I am biased, though. Perhaps these guys have changed this season and they are hitting more of these kinds of fly balls. Since 33-39 seems to be the sweet spot launch angle for increased carry distance, lets see which players are hitting the most balls on those angles, with respect to their total balls in play. I’ll also be narrowing down the search to balls hit between 80 and 105 mph, since velocities over 105 mph are much less common and those below 80 mph are too weak to be very interesting. The following shows 15 players with the greatest increase in these sweet spot launch angles. I limited this to only those with 500 PA in each of 2015 and 2016, so we’re only looking at starting players who have missed minimal playing time.
|Name||In Range 2015||In Range 2016||In Range 2015%||In Range 2015%||Difference||HR 15||HR 16||HR DIFF|
Odubel Herrera, Ian Kinsler, Curtis Granderson, Eric Hosmer, and Joey Votto top the list. Of these 15 batters, 8 have seen increases in their home run production. Murphy squeaked his way in as well, so he is definitely hitting more balls on these launch angles than he did last season. He has hit 28 this season, as opposed to 23 last season. Take note that I didn’t take care to separate out the post season, so this includes his post season heroics against the Dodgers and Cubs along with the rest of his 2015 stats. He has 5 more balls hit on these launch angles, and 4 extra home runs. These may not be causally linked, but it does give you something to think about.
The following table shows the 15 players with the largest decrease in balls hit on these angles:
|Name||In Range 2015||In Range 2016||In Range 2015%||In Range 2015%||Difference||HR15||HR16||HR DIFF|
Oddly, Asdrubal Cabrera made this list. Only six of these fifteen batters have seen decreases in home runs this season, though, with Mookie Betts and Asdrubal Cabrera having significant increases.
On its own, this launch angle/velocity window does not explain everything. Balls hit on these angles are traveling further this season, on average, compared to last season. Players who tend to hit more of these balls this season also tend to hit more home runs, but the correlation is very, very weak (~.1). Notably, these trajectories aren’t necessarily the ideal angles for home runs. They aren’t terrible for home runs, either. They have about a 20% HR/BIP. For comparison’s sake, balls hit 25-32 degrees, at these same velocities, are closer to a 28% HR/BIP rate. These 33-39 degree launch angles are your ‘less than ideal’ fly balls. Ones that you got just a tiniest bit under. Not far enough under to create a pop up, but enough for you to be, perhaps, a little frustrated. For whatever reason, these are the fly balls that are getting that 7 foot boost in distance this year.
I’ve made two more charts using Tableau showing the HR% and SLG with respect to angle and exit velocity. These charts are very similar to the distance charts up above, but these are focusing a bit more on actual game production. The charts are far too large to embed, but you can view them here.
Look at the HR% chart at the lower end of the launch angles, at the higher velocities (bottom right hand corner) and flick back and forth between 2015 and 2016 data. You’ll notice that the 2016 data is shifted up a degree. The same holds true for the higher angles as well, but I feel the lower angles are easier to spot. In fact, the whole HR% chart is shifted up about a degree.
I suppose the natural question, then, are players hitting the ball a degree higher on average? Well, not from what I can tell. In 2015, in these same ranges (87 to 105 mph, 15 to 45 degree launch angle) the average angle was 27.26 degrees. This season, 27.43 degrees. So, a small increase, but not very large. Not the 1 degree we’re seeing from that HR% chart, anyway.
All in all, looking through this data probably raises more questions than answers. Why are balls hit on the 33 to 39 degree launch angles carrying further, regardless of exit velocity? Likewise, why are balls hit on the lower 15-23 degree launch angles falling shorter? There does seem to be some correlation between players who are hitting more balls in the 33 to 39 degree launch angle window and an increase in home run rate, but the correlation is weak at best. Home runs are more often being hit at a slightly higher angle, perhaps 1 degree higher, regardless of exit velocity. An increase in exit velocity, you might assume, would increase the number of low launch angle home runs, since they could carry slightly further, but instead we’re seeing a relative drop in these lower angle home runs.
It seems to me that exit velocity alone isn’t enough to explain all of the differences I’ve noted here, although perhaps I am too naive to understand the full implications of higher exit velocities. Perhaps higher exit velocity is related to back spin on a ball, and that could account for the extra flight distances for balls hit higher into the air. Although, that relationship isn’t obvious, and I don’t have any evidence one way or the other.