best era+ by a reliever in one season at least 50 ip since 1945

Since 1945, Zack Britton has the best ERA by a relief pitcher with 50.0+ innings pitched in a season, with an ERA of 0.54 in 2016.

	NAME	ERA	IP	SEASON	TM	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	Zack Britton Z. Britton	0.54	67.0	2016	BAL	69	2	1	.667	0	74	0	0	47	38	4	7	1	18	0	63	3	254	10	9.94	2.42	4.11	0.13	29.1	7.1	0.84	.230	0.94	5.10
2	Fernando Rodney F. Rodney	0.60	74.2	2012	TBR	76	2	2	.500	0	76	0	0	48	43	5	9	2	15	3	65	1	282	4	9.16	1.81	5.07	0.24	27.0	5.3	0.78	.220	1.08	5.18
3	Emmanuel Clase E. Clase	0.61	74.1	2024	CLE	74	4	2	.667	0	66	0	0	47	39	5	10	2	10	2	66	1	270	2	7.99	1.21	6.60	0.24	24.4	3.7	0.66	.195	1.21	4.72
4	Dennis Eckersley D. Eckersley	0.61	73.1	1990	OAK	63	4	2	.667	0	73	0	0	48	41	5	9	2	4	0	61	1	262	0	8.96	0.49	18.25	0.25	27.9	1.5	0.61	.213	1.10	5.03
5	Al Benton A. Benton	0.62	58.0	1949	CLE	29	4	0	1.000	0	14	0	0	10	37	4	5	1	21	0	18		222	0	2.17	3.26	0.67	0.16	6.3	9.5	1.00	.194	0.78	5.74
6	Rob Murphy R. Murphy	0.72	50.1	1986	CIN	34	6	0	1.000	0	36	0	0	1	26	4	4	0	21	0	12	2	195	5	6.44	3.75	1.71	0.00	18.5	10.8	0.93	.188	0.72	4.65
7	Blake Treinen B. Treinen	0.78	80.1	2018	OAK	68	9	2	.818	0	100	0	0	38	46	7	12	2	21	1	58	3	315	6	11.20	2.35	4.76	0.22	31.7	6.7	0.83	.230	1.34	5.15
8	Bill Henry B. Henry	0.87	52.0	1964	CIN	37	2	2	.500	0	29	0	0	6	31	5	9	2	12	3	20	4	202	1	5.02	2.08	2.42	0.35	14.4	5.9	0.83	.186	1.56	5.37
9	Dennys Reyes D. Reyes	0.89	50.2	2006	MIN	66	5	0	1.000	0	49	0	0	0	35	5	8	3	15	0	8	2	194	4	8.70	2.66	3.27	0.53	25.3	7.7	0.99	.252	1.42	6.22
10	Junior Thompson J. Thompson	0.92	58.2	1946	NYG	38	4	5	.444	0	29	0	0	4	33	6	16	4	39	0	27		238	2	4.45	5.98	0.74	0.61	12.2	16.4	1.23	.175	2.45	5.06
11	Jonathan Papelbon J. Papelbon	0.92	68.1	2006	BOS	59	4	2	.667	0	75	0	0	35	40	7	8	3	13	1	49	2	257	2	9.88	1.71	5.77	0.40	29.2	5.1	0.78	.224	1.05	5.27
12	Wade Davis W. Davis	0.94	67.1	2015	KCR	69	8	1	.889	0	78	0	0	17	33	7	8	3	20	0	24	1	251	1	10.43	2.67	3.90	0.40	31.1	8.0	0.79	.200	1.07	4.41
13	Chris Hammond C. Hammond	0.95	76.0	2002	ATL	63	7	2	.778	0	63	0	0	0	53	8	15	1	31	1	6	9	311	1	7.46	3.67	2.03	0.12	20.3	10.0	1.11	.242	1.78	6.28
14	Eric O'Flaherty E. O'Flaherty	0.98	73.2	2011	ATL	78	2	4	.333	0	67	0	0	0	59	8	9	2	21	3	5	8	301	1	8.19	2.57	3.19	0.24	22.3	7.0	1.09	.274	1.10	7.21
15	Wade Davis W. Davis	1.00	72.0	2014	KCR	71	9	2	.818	0	109	0	0	3	38	8	8	0	23	3	11	0	279	1	13.63	2.88	4.74	0.00	39.1	8.2	0.85	.264	1.00	4.75
16	Craig Kimbrel C. Kimbrel	1.01	62.2	2012	ATL	63	3	1	.750	0	116	0	0	42	27	7	7	3	14	2	56	0	231	5	16.66	2.01	8.29	0.43	50.2	6.1	0.65	.250	1.01	3.88
17	Aaron Loup A. Loup	1.01	53.2	2021	NYM	63	6	0	1.000	0	54	0	0	0	35	6	9	1	16	4	6	0	208	0	9.06	2.68	3.38	0.17	26.0	7.7	0.95	.256	1.51	5.87
18	Dale Murray D. Murray	1.03	69.2	1974	MON	32	1	1	.500	0	31	0	0	10	46	8	12	1	23	0	23	2	271	1	4.00	2.97	1.35	0.13	11.4	8.5	0.99	.208	1.55	5.94
19	Rollie Fingers R. Fingers	1.04	78.0	1981	MIL	47	6	3	.667	0	61	0	0	28	55	9	9	3	13	1	41	5	297	1	7.04	1.50	4.69	0.35	20.5	4.4	0.87	.237	1.04	6.35
20	Chris Martin C. Martin	1.05	51.1	2023	BOS	55	4	1	.800	0	46	0	0	3	45	6	6	2	8	0	12	3	199	1	8.06	1.40	5.75	0.35	23.1	4.0	1.03	.301	1.05	7.89
21	Brad Ziegler B. Ziegler	1.06	59.2	2008	OAK	47	3	0	1.000	0	30	0	0	11	47	7	8	2	22	1	21	3	229	0	4.53	3.32	1.36	0.30	13.1	9.6	1.16	.259	1.21	7.09
22	Cla Meredith C. Meredith	1.07	50.2	2006	SDP	45	5	1	.833	0	37	0	0	0	30	6	6	3	6	2	11	3	185	0	6.57	1.07	6.17	0.53	20.0	3.2	0.71	.197	1.07	5.33
23	David Robertson D. Robertson	1.08	66.2	2011	NYY	70	4	0	1.000	0	100	0	0	1	40	8	9	1	35	1	8	6	272	6	13.50	4.72	2.86	0.14	36.8	12.9	1.13	.289	1.21	5.40
24	Koji Uehara K. Uehara	1.09	74.1	2013	BOS	73	4	1	.800	0	101	0	0	21	33	9	10	5	9	1	40	2	265	1	12.23	1.09	11.22	0.61	38.1	3.4	0.57	.188	1.21	4.00
25	Neal Cotts N. Cotts	1.11	57.0	2013	TEX	58	8	3	.727	0	65	0	0	1	36	7	8	2	18	0	6	1	223	3	10.26	2.84	3.61	0.32	29.1	8.1	0.95	.246	1.26	5.68