which pitcher had the lowest era in a month, minimum of 40 innings pitched since 1986

Since 1986, Orel Hershiser has the lowest ERA when pitching at least 40 innings in a month, with an ERA of 0.00 in September 1988.

	NAME	ERA	IP	MONTH	G	W	L	W%	GS	SO	CG	SHO	SV	H	ER	R	HR	BB	HBP	GF	IBB	TBF	WP	K/9	BB/9	K/BB	HR/9	K%	BB%	WHIP	BABIP	RA	H/9
1	Orel Hershiser O. Hershiser	0.00	55.0	September 1988	6	5	0	1.000	6	34	5	5	0	30	0	0	0	9	0	0	3	201	1	5.56	1.47	3.78	0.00	16.9	4.5	0.71	.190	0.00	4.91
2	Cory Lidle C. Lidle	0.20	45.1	August 2002	6	5	0	1.000	6	29	1	1	0	23	1	2	0	8	0	0	0	163	0	5.76	1.59	3.63	0.00	17.8	4.9	0.68	.183	0.40	4.57
3	Mike Witt M. Witt	0.21	43.0	August 1986	5	5	0	1.000	5	28	3	1	0	17	1	4	1	8	0	0	0	155	0	5.86	1.67	3.50	0.21	18.1	5.2	0.58	.136	0.84	3.56
4	Cliff Lee C. Lee	0.21	42.0	June 2011	5	5	0	1.000	5	29	3	3	0	21	1	1	0	8	0	0	0	147	0	6.21	1.71	3.63	0.00	19.7	5.4	0.69	.191	0.21	4.50
5	Jake Arrieta J. Arrieta	0.43	42.1	August 2015	6	6	0	1.000	6	43	1	1	0	19	2	4	0	10	2	0	0	159	2	9.14	2.13	4.30	0.00	27.0	6.3	0.69	.183	0.85	4.04
6	Jake Arrieta J. Arrieta	0.45	40.0	September 2015	5	4	0	1.000	5	39	1	1	0	20	2	3	1	4	1	0	0	140	1	8.78	0.90	9.75	0.23	27.9	2.9	0.60	.200	0.68	4.50
7	Johan Santana J. Santana	0.45	40.0	September 2004	6	5	0	1.000	6	52	0	0	0	20	2	2	0	7	2	0	0	146	1	11.70	1.58	7.43	0.00	35.6	4.8	0.68	.235	0.45	4.50
8	Mark Langston M. Langston	0.50	53.2	September 1988	6	5	1	.833	6	46	4	3	0	23	3	3	1	24	0	0	0	199	0	7.71	4.02	1.92	0.17	23.1	12.1	0.88	.172	0.50	3.86
9	Jack Morris J. Morris	0.54	50.0	July 1986	6	5	1	.833	6	47	4	3	0	33	3	4	1	8	0	0	1	186	3	8.46	1.44	5.88	0.18	25.3	4.3	0.82	.246	0.72	5.94
10	Javier Vazquez J. Vazquez	0.55	49.0	August 2001	6	5	1	.833	6	45	2	1	0	26	3	4	2	8	0	0	1	175	1	8.27	1.47	5.63	0.37	25.7	4.6	0.69	.200	0.73	4.78
11	Hyun Jin Ryu H. Jin Ryu	0.59	45.2	May 2019	6	5	0	1.000	6	36	1	1	0	28	3	3	0	3	0	0	0	163	0	7.09	0.59	12.00	0.00	22.1	1.8	0.68	.226	0.59	5.52
12	Martín Pérez M. Pérez	0.64	42.1	May 2022	6	4	0	1.000	6	33	1	1	0	29	3	6	0	9	0	0	0	159	2	7.02	1.91	3.67	0.00	20.8	5.7	0.90	.248	1.28	6.17
13	Pedro Martinez P. Martinez	0.64	42.1	July 2002	6	5	0	1.000	6	59	0	0	0	22	3	5	0	9	6	0	0	159	1	12.54	1.91	6.56	0.00	37.1	5.7	0.73	.259	1.06	4.68
14	Kenny Rogers K. Rogers	0.65	41.1	May 1995	6	5	1	.833	6	32	1	1	0	32	3	6	1	15	1	0	0	169	2	6.97	3.27	2.13	0.22	18.9	8.9	1.14	.258	1.31	6.97
15	Randy Johnson R. Johnson	0.66	41.0	September 2002	5	5	0	1.000	5	49	3	1	0	24	3	5	3	7	2	0	0	156	0	10.76	1.54	7.00	0.66	31.4	4.5	0.76	.221	1.10	5.27
16	Zane Smith Z. Smith	0.66	41.0	September 1990	5	3	1	.750	5	30	3	2	0	26	3	9	1	4	0	0	1	147	0	6.59	0.88	7.50	0.22	20.4	2.7	0.73	.223	1.98	5.71
17	Zac Gallen Z. Gallen	0.68	40.0	August 2022	6	5	0	1.000	6	44	0	0	0	20	3	3	0	10	1	0	0	142	0	9.90	2.25	4.40	0.00	31.0	7.0	0.75	.230	0.68	4.50
18	Doyle Alexander D. Alexander	0.71	51.0	September 1987	6	5	0	1.000	6	25	2	2	0	33	4	5	1	16	0	0	0	196	0	4.41	2.82	1.56	0.18	12.8	8.2	0.96	.208	0.88	5.82
19	Jeff D'Amico J. D'Amico	0.76	47.2	July 2000	6	5	0	1.000	6	20	1	1	0	30	4	4	3	12	1	0	0	185	1	3.78	2.27	1.67	0.57	10.8	6.5	0.88	.181	0.76	5.66
20	Ubaldo Jimenez U. Jimenez	0.78	46.0	May 2010	6	5	1	.833	6	39	1	1	0	24	4	4	1	12	3	0	0	167	2	7.63	2.35	3.25	0.20	23.4	7.2	0.78	.205	0.78	4.70
21	Chuck Finley C. Finley	0.79	45.2	May 1996	6	4	0	1.000	6	45	1	0	0	31	4	5	2	16	4	0	0	184	4	8.87	3.15	2.81	0.39	24.5	8.7	1.03	.248	0.99	6.11
22	Bill Gullickson B. Gullickson	0.79	57.0	August 1986	7	5	2	.714	7	36	3	2	0	46	5	7	2	9	0	0	1	221	1	5.68	1.42	4.00	0.32	16.3	4.1	0.96	.253	1.11	7.26
23	Jack Flaherty J. Flaherty	0.82	44.0	September 2019	6	3	1	.750	6	53	0	0	0	17	4	4	2	8	1	0	0	153	2	10.84	1.64	6.63	0.41	34.6	5.2	0.57	.169	0.82	3.48
24	Clayton Kershaw C. Kershaw	0.82	44.0	June 2014	6	6	0	1.000	6	61	2	1	0	26	4	4	2	4	0	0	0	162	2	12.48	0.82	15.25	0.41	37.7	2.5	0.68	.253	0.82	5.32
25	Felix Hernandez F. Hernandez	0.82	43.2	August 2010	6	3	2	.600	6	51	0	0	0	30	4	11	3	13	0	0	1	172	3	10.51	2.68	3.92	0.62	29.7	7.6	0.98	.257	2.27	6.18