Ed Cushman has the best ERA- in a season, with an ERA- of 8 in 1884.

Interpreted as:

best era - with a minimum of 1 IP per team game in a season by a pitcher

	NAME	ERA-	SEASON	TM	G	W	L	W%	GS	ERA	SO	CG	SHO	SV	IP	H	ER	R	HR	BB	HBP	GF	IBB	TBF	WP	K/9	BB/9	K/BB	HR/9	K%	BB%	WHIP	BABIP	RA	FIP	FIP-	H/9	PRAA
1	Ed Cushman E. Cushman	8	1884	MIL	4	4	0	1.000	4	1.00	47	4	2	0	36.0	10	4	4	0	3		0		125	1	11.75	0.75	15.67	0.00	37.6	2.4	0.36		1.00	0.91	8	2.50	17.4
2	Lady Baldwin L. Baldwin	20	1884	MIL	2	1	1	.500	2	2.65	21	2	0	0	17.0	7	5	5	0	1		0		61	0	11.12	0.53	21.00	0.00	34.4	1.6	0.47		2.65	0.98	9	3.71	8.2
3	Henry Porter H. Porter	23	1884	MIL	6	3	3	.500	6	3.00	71	6	1	0	51.0	32	17	25	1	9		0		200	6	12.53	1.59	7.89	0.18	35.5	4.5	0.80		4.41	1.27	11	5.65	24.1
4	Dan Casey D. Casey	32	1884	WIL	2	1	1	.500	2	1.00	10	2	0	0	18.0	23	2	17	0	4		0		83	0	5.00	2.00	2.50	0.00	12.0	4.8	1.50		8.50	2.83	104	11.50	-0.1
5	Tim Keefe T. Keefe	35	1880	TRO	12	6	6	.500	12	0.86	39	12	0	0	105.0	68	10	27	0	16		0		397	1	3.34	1.37	2.44	0.00	9.8	4.0	0.80		2.31	2.25	91	5.83	3.6
6	Pedro Martinez P. Martinez	35	2000	BOS	29	18	6	.750	29	1.74	284	7	4	0	217.0	128	42	44	17	32	14	0	0	817	1	11.78	1.33	8.88	0.71	34.8	3.9	0.74	.236	1.82	2.16	47	5.31	61.5
7	Dutch Leonard D. Leonard	36	1914	BSA	36	19	5	.792	25	0.96	176	17	7	3	224.2	139	24	34	3	60	8	8		842	2	7.05	2.40	2.93	0.12	20.9	7.1	0.89	.229	1.36	1.95	70	5.57	20.4
8	Trevor Bauer T. Bauer	36	2020	CIN	11	5	4	.556	11	1.73	100	2	2	0	73.0	41	14	17	9	17	3	0	1	278	3	12.33	2.10	5.88	1.11	36.0	6.1	0.79	.215	2.10	2.87	61	5.05	14.1
9	Greg Maddux G. Maddux	37	1994	ATL	25	16	6	.727	25	1.56	156	10	3	0	202.0	150	35	44	4	31	6	0	3	774	3	6.95	1.38	5.03	0.18	20.2	4.0	0.90	.253	1.96	2.39	55	6.68	43.7
10	Shane Bieber S. Bieber	37	2020	CLE	12	8	1	.889	12	1.63	122	0	0	0	77.1	46	14	15	7	21	1	0	0	297	5	14.20	2.44	5.81	0.81	41.1	7.1	0.87	.267	1.75	2.06	46	5.35	20.5
11	Bob Gibson B. Gibson	38	1968	STL	34	22	9	.710	34	1.12	268	28	13	0	304.2	198	38	49	11	62	7	0	6	1,161	4	7.92	1.83	4.32	0.32	23.1	5.3	0.85	.230	1.45	1.77	63	5.85	34.8
12	Greg Maddux G. Maddux	39	1995	ATL	28	19	2	.905	28	1.63	181	10	3	0	209.2	147	38	39	8	23	4	0	3	785	1	7.77	0.99	7.87	0.34	23.1	2.9	0.81	.244	1.67	2.25	52	6.31	46.9
13	Walter Johnson W. Johnson	39	1913	WSH	48	36	7	.837	36	1.14	243	29	11	2	346.0	232	44	56	9	38	9	10		1,271	2	6.32	0.99	6.39	0.23	19.1	3.0	0.78	.229	1.46	1.90	63	6.03	42.3
14	Mordecai Brown M. Brown	39	1906	CHC	36	26	6	.813	32	1.04	144	27	9	3	277.1	198	32	56	1	61	4	4		1,044	2	4.67	1.98	2.36	0.03	13.8	5.8	0.93	.236	1.82	2.08	75	6.43	21.1
15	Frank Killen F. Killen	41	1891	MIL	11	7	4	.636	11	1.68	38	11	2	0	96.2	73	18	42	1	51	3	0		415	4	3.54	4.75	0.75	0.09	9.2	12.3	1.28	.224	3.91	3.55	90	6.80	6
16	Walter Johnson W. Johnson	42	1912	WSH	50	33	12	.733	37	1.39	303	34	7	2	369.0	259	57	89	2	76	16	13		1,413	11	7.39	1.85	3.99	0.05	21.4	5.4	0.91	.253	2.17	2.03	63	6.32	49.6
17	Pedro Martinez P. Martinez	42	1999	BOS	31	23	4	.852	29	2.07	313	5	1	0	213.1	160	49	56	9	37	9	1	1	835	6	13.20	1.56	8.46	0.38	37.5	4.4	0.92	.323	2.36	1.38	30	6.75	79.4
18	Christy Mathewson C. Mathewson	42	1905	NYG	43	31	9	.775	37	1.28	206	32	8	3	338.2	252	48	85	4	64	1	6		1,294	6	5.47	1.70	3.22	0.11	15.9	4.9	0.93	.243	2.26	2.03	69	6.70	34.9
19	Grover Alexander G. Alexander	43	1915	PHN	49	31	10	.756	42	1.22	241	36	12	3	376.1	253	51	86	3	64	10	7		1,435	2	5.76	1.53	3.77	0.07	16.8	4.5	0.84	.224	2.06	1.82	63	6.05	44.1
20	Dwight Gooden D. Gooden	44	1985	NYM	35	24	4	.857	35	1.53	268	16	8	0	276.2	198	47	51	13	69	2	0	4	1,065	6	8.72	2.24	3.88	0.42	25.2	6.5	0.97	.259	1.66	2.12	59	6.44	45.6
21	Christy Mathewson C. Mathewson	44	1909	NYG	37	25	6	.806	33	1.14	149	26	8	2	275.1	192	35	57	2	36	0	4		998	4	4.87	1.18	4.14	0.07	14.9	3.6	0.83	.234	1.86	1.62	61	6.28	31.7
22	Zack Greinke Z. Greinke	44	2015	LAD	32	19	3	.864	32	1.66	200	1	0	0	222.2	148	41	43	14	40	5	0	1	843	7	8.08	1.62	5.00	0.57	23.7	4.7	0.84	.229	1.74	2.75	73	5.98	26.2
23	Cy Young C. Young	44	1901	BSA	43	33	10	.767	41	1.62	158	38	5	0	371.1	324	67	112	6	37	7	2		1,440	2	3.83	0.90	4.27	0.15	11.0	2.6	0.97	.258	2.71	2.64	72	7.85	42.6
24	Roger Clemens R. Clemens	44	2005	HOU	32	13	8	.619	32	1.87	185	1	0	0	211.1	151	44	51	11	62	3	0	5	838	3	7.88	2.64	2.98	0.47	22.1	7.4	1.01	.243	2.17	2.86	67	6.43	33.4
25	Jacob deGrom J. deGrom	44	2018	NYM	32	10	9	.526	32	1.70	269	1	0	0	217.0	152	41	48	10	46	5	0	3	835	2	11.16	1.91	5.85	0.41	32.2	5.5	0.91	.281	1.99	1.98	50	6.30	49