14 July 2016

Matt Wieters HR Hypothesis: Blame Millenial Pitchers' Lack of Self Control

Yesterday, I heard about Matt Wieters' hypothesis about why home runs are up to potentially record breaking numbers after years of power decline.  His thought was that pitchers were being aggressively promoted as a result of fastball velocity as opposed to being able to master command of their pitches.  In other words, pitch locations were wobbling well away from the intended target and getting clobbered.  Cynically, this would be an argument a catcher might make to explain why a pitcher is at fault with a focus on pitchers with no seniority.

To test better conceptualize that, I put together a series of graphs showing home run per fly ball rates from 2008 until 2016.  If mistakes are the issue, then one would expect an increase in that rate as more pitches are squared up on.  Second, if this was an age issue, then that would become evident.  Historically, there are no significant differences between age groups.


The above graph makes it clear that all age groups have seen a major increase in home runs per fly ball.  It simply is not a youth issue and one would suspect that very few players above the age of 31 are without much experience at the MLB level.  I next broke this out into starters and relievers (not shown).  The rate follow the same shape, but with relievers 0.5 to 1.0 % fewer HR/FL than starters.  No significant differences were found for any age group for either relievers or starters.

To gauge how much of an increase we are discussing here compared to the historical (2008-2015) mean, I graphed each age group and separated them by starters and relievers.


There is a U shape here where younger and older pitchers have been more aversely impacted with HR/FL increase in rates.  Again though, all groups have observed significantly higher HR/FL rates.

With these graphs in mind, it is difficult to see much beyond the Wieters' hypothesis about poorly experienced arms making everyone look bad (or good, depending on your point of view).  After writing this up, the Washington Post took some aims at answering whether Wieters was right.  They looked into whether more home runs are being hit (they are), whether fastball velocity has increased (it has, which we have known for quite a while and actually wrote the seminal piece several years ago on this site), whether more mistake pitches down the middle are being hit for home runs (yes, which tracks with more home runs overall being hit though), and whether young pitchers are at fault (not beyond historical norms).

While looking at the batted ball data, the differences are not much and do not appear to be significant.  However, it seems that this noisy data might suggest that there is more hard hit contact and that it siphoned it from the medium hit group.

Season
Soft%
Med%
Hard%
2008
17
56
27
2009
16
57
27
2010
18
52
30
2011
24
52
24
2012
16
56
28
2013
17
53
30
2014
18
53
29
2015
19
53
28
2016
19
50
31
 
 
 
 
 Maybe this means that players are squaring up on the ball better.  I do not know.

Another idea is that perhaps teams are embracing more uppercut style hitters as the league embraces more groundball pitching.  How does that pan out?

Season
LD%
GB%
FB%
2008
20
44
36
2009
19
43
38
2010
18
44
38
2011
20
44
36
2012
21
45
34
2013
21
45
34
2014
21
45
34
2015
21
45
34
2016
21
45
34

 Honestly, if you had told me that the last five years have resulted in a leveling off of batted ball profiles and that we are seeing levels lowers than the pre-PED testing era.  All in all, I am at a bit of a loss.  Perhaps teams and players are more effective with changing swing planes, but I am doubtful of that.  Perhaps the ball is both legal and accidentally a little juiced this year.  Regardless, I do not think Wieters' hypothesis about millennial pitchers works.

5 comments:

Roger said...

Maybe it applies to the Orioles pitchers that he's catching more than to the league overall......

Jon Shepherd said...

Maybe, but the Orioles have not exactly been promoting high velocity guys. Regardless, his hypothesis as he applies it to the whole league is a dog that won't hunt.

Benjamin Stoehr said...

The jaded cynic in me believes that the increase in home runs is probably attributable to the players finally having figured out which PEDs don't show up on tests.

Jon Shepherd said...

PEDs have always been a rather poor explanation for home run hitting. The 90s saw a large immediate increase in, I believe, 1994. It was not as if players were not using and then all of a sudden were using. Likewise, the jump this year from last would be weird to lay at the feet of PED use. Behavior in a population takes time for individuals to adapt and incorporate. It simply is not a switch. Major changes come from slight changes to the ball, large scale weather phenomena, and large scale adaptation (which typically takes about 3 years as evidenced by such changes in strategy like shifts). PEDs simply are not a great explainer when you get down to what we are seeing and the mechanism required for large scale and immediate PED abuse.

Benjamin Stoehr said...

I'm actually inclined to agree with you. Like I said, it was just the jaded cynic in me. How about teams being more willing to play guys with no glove who strike out a lot but can hit a ton? It doesn't explain a one year jump, I'm guessing that has something to do with this year's ball and some manufacturing difference, but there do seem to be more of those guys around. Could just be that I'm an Os fan though.