Les Sweetland has the highest ERA in a season, with an ERA of 7.71 in 1930.

Interpreted as:

highest career era with a minimum of 1 IP per team game by a player + in a single season

	NAME	ERA	SEASON	TM	G	W	L	W%	GS	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	ERA-	FIP	FIP-	H/9	PRAA
1	Les Sweetland L. Sweetland	7.71	1930	PHN	34	7	15	.318	25	36	8	1	0	167.0	271	143	164	24	60	5	5		817	0	1.94	3.23	0.60	1.29	4.4	7.3	1.98	.357	8.84	141	6.11	113	14.60	-10.3
2	William Rotes W. Rotes	7.60	1893	LOU	20	5	12	.294	19	22	17	0	0	151.2	244	128	173	10	66	10	1		769	1	1.31	3.92	0.33	0.59	2.9	8.6	2.04	.354	10.27	170	5.31	119	14.48	-16.2
3	Jack Wadsworth J. Wadsworth	7.60	1894	LOU	22	4	18	.182	22	57	20	0	0	173.0	261	146	204	10	103	4	0		866	13	2.97	5.36	0.55	0.52	6.6	11.9	2.10	.363	10.61	149	5.76	113	13.58	-14.9
4	Jim Deshaies J. Deshaies	7.39	1994	MIN	25	6	12	.333	25	78	0	0	0	130.1	170	107	109	30	54	2	0	0	596	1	5.39	3.73	1.44	2.07	13.1	9.1	1.72	.324	7.53	151	6.21	131	11.74	-21.3
5	Jack Knott J. Knott	7.29	1936	SLA	47	9	17	.346	23	60	9	0	6	192.2	272	156	174	15	93	4	16		929	11	2.80	4.34	0.65	0.70	6.5	10.0	1.89	.339	8.13	138	5.16	102	12.71	-1.5
6	Tom Colcolough T. Colcolough	7.23	1894	PIT	23	8	5	.615	14	29	11	0	0	150.2	213	121	147	5	72	5	8		724	7	1.73	4.30	0.40	0.30	4.0	9.9	1.89	.339	8.78	140	5.39	104	12.72	-5.1
7	Jose Lima J. Lima	6.99	2005	KCR	32	5	16	.238	32	80	1	0	0	168.2	219	131	140	31	61	9	0	1	780	5	4.27	3.25	1.31	1.65	10.3	7.8	1.66	.314	7.47	156	5.70	132	11.69	-25.8
8	Frank Bates F. Bates	6.90	1899	TOT	22	1	18	.053	19	13	17	0	0	161.2	246	124	183	6	110	23	3		839	5	0.72	6.12	0.12	0.33	1.5	13.1	2.20	.349	10.19	179	5.73	149	13.69	-33.8
9	Harry Staley H. Staley	6.81	1894	BSN	27	12	10	.545	21	32	18	0	1	208.2	305	158	204	15	61	5	6		972	4	1.38	2.63	0.52	0.65	3.3	6.3	1.75	.338	8.80	122	5.39	96	13.15	7.1
10	Matthew Boyd M. Boyd	6.71	2020	DET	12	3	7	.300	12	60	1	0	0	60.1	67	45	46	15	22	5	0	0	271	5	8.95	3.28	2.73	2.24	22.1	8.1	1.48	.308	6.86	153	5.77	131	9.99	-9.3
11	LaTroy Hawkins L. Hawkins	6.66	1999	MIN	33	10	14	.417	33	103	1	0	0	174.1	238	129	136	29	60	1	0	2	803	9	5.32	3.10	1.72	1.50	12.8	7.5	1.71	.343	7.02	133	5.15	109	12.29	-8.1
12	Jose Lima J. Lima	6.65	2000	HOU	33	7	16	.304	33	124	0	0	0	196.1	251	145	152	48	68	2	0	3	895	3	5.68	3.12	1.82	2.20	13.9	7.6	1.62	.311	6.97	138	6.11	129	11.51	-29.2
13	Greg Harris G. Harris	6.65	1994	COL	29	3	12	.200	19	82	1	0	1	130.0	154	96	99	22	52	5	2	4	588	5	5.68	3.60	1.58	1.52	13.9	8.8	1.58	.309	6.85	138	5.38	121	10.66	-12.7
14	Chubby Dean C. Dean	6.61	1940	PHA	30	6	13	.316	19	38	8	1	1	159.1	220	117	136	21	63	0	8		754	5	2.15	3.56	0.60	1.19	5.0	8.4	1.78	.315	7.68	149	5.26	121	12.43	-16.1
15	Darryl Kile D. Kile	6.61	1999	COL	32	8	13	.381	32	116	1	0	0	190.2	225	140	150	33	109	6	0	5	888	13	5.48	5.15	1.06	1.56	13.1	12.3	1.75	.308	7.08	119	5.97	117	10.62	-16.2
16	Nels Potter N. Potter	6.60	1939	PHA	41	8	12	.400	25	60	9	0	2	196.1	258	144	163	26	88	5	12		922	12	2.75	4.03	0.68	1.19	6.5	9.5	1.76	.312	7.47	143	5.50	124	11.83	-22.9
17	Tony Mullane T. Mullane	6.59	1894	TOT	25	7	11	.389	19	46	12	0	4	155.2	201	114	152	7	100	7	6		756	12	2.66	5.78	0.46	0.40	6.1	13.2	1.93	.326	8.79	121	5.87	108	11.62	-6.3
18	Ernie Wingard E. Wingard	6.56	1927	SLA	38	2	13	.133	17	28	7	0	0	156.1	213	114	132	7	79	2	11		738	8	1.61	4.55	0.35	0.40	3.8	10.7	1.87	.331	7.60	153	4.80	113	12.26	-8.5
19	George Caster G. Caster	6.56	1940	PHA	36	4	19	.174	24	75	11	0	2	178.1	234	130	160	18	69	3	8		835	3	3.79	3.48	1.09	0.91	9.0	8.3	1.70	.322	8.07	148	4.52	104	11.81	-3.5
20	Sandy Alcantara S. Alcantara	6.55	2025	MIA	23	6	11	.353	23	90	0	0	0	121.0	129	88	90	15	47	6	0	0	536	7	6.69	3.50	1.91	1.12	16.8	8.8	1.45	.302	6.69	153	4.54	111	9.60	-5.9
21	George Keefe G. Keefe	6.52	1890	BUF	25	6	16	.273	22	55	22	0	0	196.0	280	142	229	11	138	5	3		1,014	13	2.53	6.34	0.40	0.51	5.4	13.6	2.13	.334	10.52	157	5.27	128	12.86	-26.7
22	Scott Stratton S. Stratton	6.51	1894	TOT	23	9	10	.474	18	27	16	0	0	171.1	277	124	181	8	55	6	4		832	5	1.42	2.89	0.49	0.42	3.2	6.6	1.94	.365	9.51	121	5.17	96	14.55	5.3
23	Bill Kissinger B. Kissinger	6.51	1895	TOT	26	5	12	.294	16	34	10	0	0	152.0	240	110	156	8	53	8	10		742	3	2.01	3.14	0.64	0.47	4.6	7.1	1.93	.363	9.24	138	5.02	106	14.21	-5.3
24	Terry Mulholland T. Mulholland	6.49	1994	NYY	24	6	7	.462	19	72	2	0	0	120.2	150	87	94	24	37	3	4	1	542	5	5.37	2.76	1.95	1.79	13.3	6.8	1.55	.310	7.01	138	5.51	116	11.19	-10.4
25	Bill Kissinger B. Kissinger	6.49	1896	STL	20	2	9	.182	12	22	11	0	1	136.0	209	98	136	5	55	8	7		662	4	1.46	3.64	0.40	0.33	3.3	8.3	1.94	.357	9.00	147	4.84	110	13.83	-6.2