Poll 2015: Which Group of Pitchers Performs Better?

In 2013, I began polling you readers on which group of pitchers you think will post the better aggregate ERA post all-star break. The two groups were determined based on ERA-SIERA disparity, pitting the underperformers versus the overperformers during the pre-all-star break period. You can view the results of the first experiment here. For some strange reason, it appears I never actually calculated the results of last year’s experiment, but here was the original poll.

I came up with this idea given my faith in using SIERA over smaller samples, rather than ERA. I generally ignore ERA completely during the middle of the season and it’s interesting to see how everyone else thinks. Will the SIERA outperformers continue to outperform, perhaps due to continued strong defensive support or will the magic vanish? And is it just bad luck that is due to reverse course for the SIERA underperformers or are they being hurt by something that should continue to play a role the rest of the way?

My population group consisted of 97 qualified starters, which included some that are no longer in a rotation. I have decided to only include those who will remain a starter. Group A is composed of the 10 largest SIERA outperformers, while Group B is composed of the 10 largest SIERA underperformers.

Group A – The SIERA Outperformers

Name	IP	ER	K%	BB%	BABIP	LOB%	HR/FB	ERA	SIERA	ERA-SIERA
Chris Young	87	29	16.0%	6.9%	0.212	77.3%	6.9%	3.00	4.80	-1.80
Zack Greinke	123.1	19	22.8%	4.3%	0.233	89.5%	6.3%	1.39	3.17	-1.78
Hector Santiago	108.1	28	22.0%	7.6%	0.244	88.9%	8.4%	2.33	3.95	-1.62
Yovani Gallardo	113.1	33	16.8%	8.5%	0.267	77.4%	6.6%	2.62	4.22	-1.60
Shelby Miller	113.2	30	20.4%	7.5%	0.276	78.8%	5.9%	2.38	3.73	-1.35
Nick Martinez	97	37	13.4%	8.0%	0.286	76.3%	9.3%	3.43	4.76	-1.33
A.J. Burnett	119.1	28	20.5%	6.8%	0.314	81.7%	4.7%	2.11	3.43	-1.32
Sonny Gray	123.2	28	22.4%	6.2%	0.249	79.0%	4.8%	2.04	3.25	-1.21
Kyle Gibson	113.2	36	16.7%	7.7%	0.268	80.6%	13.4%	2.85	3.95	-1.10
Scott Kazmir	101.1	28	23.3%	8.3%	0.265	77.2%	7.9%	2.49	3.59	-1.10
Total	1100.2	296	19.6%	7.1%	0.262	80.9%	7.3%	2.42	3.84	-1.42

Group B – The SIERA Underperformers

Name	IP	ER	K%	BB%	BABIP	LOB%	HR/FB	ERA	SIERA	ERA-SIERA
Kyle Lohse	108	74	17.0%	4.9%	0.312	64.2%	15.4%	6.17	4.07	2.10
Rick Porcello	100.2	66	18.1%	5.3%	0.331	64.8%	14.5%	5.90	3.86	2.04
CC Sabathia	100.1	61	19.3%	4.6%	0.332	69.0%	17.1%	5.47	3.65	1.82
Drew Hutchison	98	58	21.0%	6.9%	0.358	65.2%	9.7%	5.33	3.75	1.58
Rubby de la Rosa	110.1	62	21.1%	6.2%	0.299	70.6%	20.2%	5.06	3.51	1.55
Carlos Carrasco	108.1	49	27.7%	5.2%	0.339	70.3%	11.0%	4.07	2.73	1.34
Taijuan Walker	102.1	55	22.9%	6.2%	0.307	68.9%	13.1%	4.84	3.50	1.34
Matt Garza	99	61	15.3%	7.4%	0.317	65.3%	16.0%	5.55	4.38	1.17
Jeremy Hellickson	94.2	53	19.4%	6.6%	0.309	69.2%	11.6%	5.04	3.91	1.13
Kyle Kendrick	103	68	12.0%	6.4%	0.287	70.3%	16.8%	5.94	4.89	1.05
Total	1024.2	607	19.4%	6.0%	0.319	67.8%	14.6%	5.33	3.82	1.52

Amazingly, the two groups have nearly identical SIERA marks, but a nearly three run difference in ERA. The outperformers have exactly half the HR/FB rate as the underperformers, along with a lower BABIP and significantly higher LOB%.