Did the 2014 strike zone change help GB pitchers?

[PrometheusWakefield]

This has been mentioned in a couple of threads on the Red Sox thinking this offseason, and I thought it was worthy of a more comprehensive analysis than I had seen to date. 
 
As many know, the strike zone looked a little different in 2014 than it did in 2013. I'll quote the New York Times from this October on the subject:
 

The strike zone is bigger than it used to be, especially around batters’ knees.
 
The change appears to stem from the league’s growing use of video technology to evaluate umpires, which has led umpires to stick more closely to the official strike zone. And according to the rule book, the strike zone extends down to “the hollow beneath the kneecap.” The enlarged strike zone, in turn, seems to be a major reason that strikeouts have risen and scoring has dropped sharply.
 

Two different analyses of pitch-tracking software have found that the strike zone has grown almost 10 percent over the last five years. It grew in each of the last five seasons and more in 2014 than in any previous season. Five years ago, pitches just below 21 inches high and over the plate were rarely called strikes. This season, they usually were, according to one of the analyses, by Jon Roegele, which appeared in the publication Hardball Times.
 
“The strike zone has increased in size significantly,” said Brian Mills, a professor of sports management at the University of Florida, and the author of the other analysis, “and it’s had a huge impact on run scoring over the past eight years or so.”

 

 

The general decline of offense in favor of pitching is one obvious consequence of an enlarged strike zone, but having it the strike zone expand the lower part of the zone should also benefit certain kinds of pitchers over others. Specifically, the low strike zone should work to the benefit of low in the zone, ground ball pitchers. That is, the kind of pitchers the Red Sox have been acquiring this offseason.
 
A secondary question is how the impact of increased use of defensive shifts might have an impact on the performance of ground ball pitchers. Are ground ball pitchers disproportionately benefiting from shifts?
 
So I thought I'd take a look at the top groundball pitchers in baseball and see if, as a group, they had significantly achieved an improvement in their performance between 2013 and 2014. Here are all the pitchers in MLB who had a 53% GB rate in 2014 and had enough innings in 2013 to provide a decent enough sample for that year:
 

Top GB pitchers, 2014

2014
	ERA	FIP	K/9	BB/9	HR/9	GB%
Keuchel	2.93	3.2	6.57	2.16	0.5	63.5
Ross	3.17	3.11	8.97	3.31	0.6	57
Hernandez	2.14	2.51	9.46	1.75	0.61	56.2
Cobb	2.87	3.33	8.06	2.54	0.6	56.2
Liriano	3.02	3.4	9.7	4.49	0.72	54.4
Wheeler	3.54	3.49	9.08	3.84	0.68	54
Alvarez	2.65	3.57	5.34	1.59	0.67	53.8
Peralta	3.53	3.64	6.98	2.76	1.04	53.6
Leake	3.7	3.49	6.89	2.1	0.97	53.4
Hudson	3.57	3.57	5.7	1.62	0.71	53.1

 
Here are those same pitchers during 2013:
 
 

2014 GB% leaders in 2013

2013
	ERA	FIP	K/9	BB/9	HR/9	GB%
Keuchel	5.15	4.25	7.2	3.05	1.17	55.8
Ross	3.17	3.43	8.57	3.17	0.58	54.9
Hernandez	3.04	2.66	9.51	2.03	0.66	51.4
Cobb	4.03	3.02	8.41	2.83	0.82	55.8
Liriano	3.02	3.12	9.11	3.52	0.5	50.5
Wheeler	3.42	3.49	7.56	4.14	0.9	43.2
Alvarez	3.59	3.97	5	2.37	0.18	53.5
Peralta	4.37	4.13	6.33	3.58	0.93	51
Leake	3.37	3.91	5.71	2.25	0.98	48.7
Hudson	3.97	3.56	6.51	2.47	0.69	55.8

 
Here is the difference between their 2014 performance and their 2013 performance, in %
 

Difference between 2014 and 2013

Difference
	ERA	FIP	K/9	BB/9	HR/9	GB%
Keuchel	57	75	91	71	43	114
Ross	100	91	105	104	103	104
Hernandez	70	94	99	86	92	109
Cobb	71	110	96	90	73	101
Liriano	100	109	106	128	144	108
Wheeler	104	100	120	93	76	125
Alvarez	74	90	107	67	372	101
Peralta	81	88	110	77	112	105
Leake	110	89	121	93	99	110
Hudson	90	100	88	66	103	95
Average	86	95	104	87	122	107

 
 
Overall, ERA improved by 14% from 2013 to 2014, while xFIP improved a more modest 5%. K/9 improved 4%, but BB/9 had the biggest impact - exactly what you'd be looking for for strike zone differences, with a 13% drop in BB/9. This chart has HR/9 jumping by 22% as well, although all of that jump comes from Henderson Alvarez, whose HR/9 jumped from an obviously unsustainable .18 in 2013 to .66 in 2014. Remove Alvarez and the HR/9 rate of the others improved by 6%.
 
It's too limited a set of data to draw firm conclusions, but a 13% drop in BB/9 spread out among a pretty significant set of starters seems significant, although there may be a little bit of selection bias. I'm particularly impressed at the number of starters who went from having good control to great control. Keutchel drops by 95 points, Alvarez from 2.37 to 1.59, Hudson from 2.47 to 1.62. Hernandez from 2.03 to 1.75. Only the erratic Liriano moves significantly in the other direction on BB/9.
 
I think these numbers could also suggest that shifts could be having some impact. Out of the 10 pitchers 5 had ERAs that outperformed their xFIP, with only Leake going significantly the other way. You look at the teams that employ the most defensive shifts and I see some overlap with the pitchers with good differentials there although the relationship isn't clear.

 

[barbed wire Bob]

I don't know where else to put this but I wonder if the configuration of Fenway park also comes into consideration.  Historically, Fenway has been a pitchers park and, according to Bill James, Fenway has a Runs Index of 115.  Also, Fenway is second only to Coors Field in allowing the fewest foul outs and, according to this article on Fangraphs, Fenway inflates run-scoring on flyballs second only to Coors Field largely due to the Monster.   In the past,  teams constructed their position-player roster to take advantage of the park factors but I wonder if the Red Sox are exploiting a  new market inefficiency by targeting ground ball pitchers.

 

[charlieoscar]

I didn't feel like going through all the numbers but using bb-ref's league batting splits (MLB) vs. Ground Ball/Fly Ball Pitchers:
 
2014 -- .252/.317/.370/.686
2013 -- .259/.325/.382/.706, where Ground Ball are in the bottom third of the league in the ratio of fly ball outs to ground ball outs. Stats are based on the three years before and three years after (when available), and the season for when the split is computed, i.e., 2013 covers 2010-14 and 2014 covers 2011-2014. In other words, the drop in offense over this rime has some bearing, does it not? I don't know how much weight to give to the strike zone change.

 

[67WasBest]

Nice work on the topic and table.  I've been wondering why we never saw these kinds of numbers from Keuchel in his ml years?  Keuchel's gain in GBs coincides with drops in K and BB rates.  Looks like his critical moment pitch was taken more in 2013, and some were K's, while others were balls.  In 2014, and with the league wide recognition of the lower strike zone, those same critical moment pitches, thrown to the same locations, and thrown the same way as in 2013, were swung at more often and generated more ground balls.
 
It may well be there are many more hidden gems in the minors as they continue to adjust to the low zone MLB used in 2014.  If anyone knows that ml baseball has already started that process, or completed same, that would be worthwhile to know.
 
With defensive shifts, especially to the right side, and an ability to consistently locate a pitch, with late movement on that low outside corner, these guys have greater value.  Loading up a team with all this type pitcher makes great sense in the near term while the zone is as it is.  It could set them up for a less than desired outcome if MLB were to adjust the strike zone higher in an effort to raise offense.  Unlikely in the near term, but if the trend to defense and pitching continues to lower offense, they will have to do something in maybe 3 to 5 years time, so I suspect their desired pitching deals to remain in the 3 year window, with league minimum preferred even more.

 

[nvalvo]

It could set them up for a less than desired outcome if MLB were to adjust the strike zone higher in an effort to raise offense. 

 
It seems unlikely to me that the league is simultaneously looking to boost offense *and* shorten games.