Mariano Rivera has the lowest career ERA in the postseason when pitching at least 30 innings, with an ERA of 0.70.

Interpreted as:

lowest era by a player in MLB postseason min 30 ip

	NAME	ERA	IP	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	Mariano Rivera M. Rivera	0.70	141.0	96	8	1	.889	0	110	0	0	42	86	11	13	2	21	3	78	4	527	3	7.02	1.34	5.24	0.13	20.9	4.0	0.76	.215	0.83	5.49
2	Harry Brecheen H. Brecheen	0.83	32.2	7	4	1	.800	3	18	3	1	0	28	3	3	0	12	0	4	3	129	0	4.96	3.31	1.50	0.00	14.0	9.3	1.22	.283	0.83	7.71
3	Jeremy Affeldt J. Affeldt	0.86	31.1	33	2	0	1.000	0	20	0	0	0	14	3	3	1	8	2	4	2	111	2	5.74	2.30	2.50	0.29	18.0	7.2	0.70	.163	0.86	4.02
4	Babe Ruth B. Ruth	0.87	31.0	3	3	0	1.000	3	8	2	1	0	19	3	3	1	10	1	0	0	116	1	2.32	2.90	0.80	0.29	6.9	8.6	0.94	.188	0.87	5.52
5	Sherry Smith S. Smith	0.89	30.1	3	1	2	.333	3	5	3	0	0	17	3	4	0	9	0	0	1	110	0	1.48	2.67	0.56	0.00	4.5	8.2	0.86	.177	1.19	5.04
6	Andrew Miller A. Miller	0.93	38.2	29	2	1	.667	0	54	0	0	1	20	4	4	3	13	3	3	2	148	1	12.57	3.03	4.15	0.70	36.5	8.8	0.85	.227	0.93	4.66
7	Sandy Koufax S. Koufax	0.95	57.0	8	4	3	.571	7	61	4	2	0	36	6	10	2	11	0	0	1	213	0	9.63	1.74	5.55	0.32	28.6	5.2	0.82	.245	1.58	5.68
8	Monte Pearson M. Pearson	1.01	35.2	4	4	0	1.000	4	28	3	1	0	19	4	5	1	7	0	0	0	133	0	7.07	1.77	4.00	0.25	21.1	5.3	0.73	.186	1.26	4.79
9	Christy Mathewson C. Mathewson	1.06	101.2	11	5	5	.500	11	48	10	4	0	76	12	22	1	10	1	0	3	391	1	4.25	0.89	4.80	0.09	12.3	2.6	0.85	.227	1.95	6.73
10	Blue Moon Odom B. Moon Odom	1.13	39.2	10	3	1	.750	4	27	1	1	0	22	5	7	0	13	0	1	0	150	2	6.13	2.95	2.08	0.00	18.0	8.7	0.88	.200	1.59	4.99
11	Ian Anderson I. Anderson	1.26	35.2	8	4	0	1.000	8	40	0	0	0	20	5	5	1	17	2	0	0	145	1	10.09	4.29	2.35	0.25	27.6	11.7	1.04	.224	1.26	5.05
12	Eddie Plank E. Plank	1.32	54.2	7	2	5	.286	6	32	6	0	0	36	8	11	0	11	4	1	1	215	1	5.27	1.81	2.91	0.00	14.9	5.1	0.86	.214	1.81	5.93
13	Bill Hallahan B. Hallahan	1.36	39.2	7	3	1	.750	5	27	3	2	1	29	6	6	0	23	1	1	1	172	1	6.13	5.22	1.17	0.00	15.7	13.4	1.31	.240	1.36	6.58
14	Clay Carroll C. Carroll	1.39	32.1	22	4	2	.667	0	22	0	0	2	24	5	5	1	13	0	8	4	129	0	6.12	3.62	1.69	0.28	17.1	10.1	1.14	.247	1.39	6.68
15	Ranger Suárez R. Suárez	1.43	37.2	10	3	1	.750	8	40	0	0	1	27	6	7	2	12	1	1	0	153	0	9.56	2.87	3.33	0.48	26.1	7.8	1.04	.255	1.67	6.45
16	Stephen Strasburg S. Strasburg	1.46	55.1	9	6	2	.750	8	71	0	0	0	44	9	13	4	8	1	0	1	218	1	11.55	1.30	8.88	0.65	32.6	3.7	0.94	.299	2.11	7.16
17	Mickey Lolich M. Lolich	1.57	46.0	5	3	1	.750	5	31	3	0	0	34	8	9	3	11	1	0	0	180	0	6.07	2.15	2.82	0.59	17.2	6.1	0.98	.231	1.76	6.65
18	George Earnshaw G. Earnshaw	1.58	62.2	8	4	3	.571	8	56	5	1	0	39	11	14	2	17	0	0	1	245	1	8.04	2.44	3.29	0.29	22.9	6.9	0.89	.218	2.01	5.60
19	Cy Young C. Young	1.59	34.0	4	2	1	.667	3	17	3	0	0	31	6	13	1	4	1	1	0	142	0	4.50	1.06	4.25	0.26	12.0	2.8	1.03	.252	3.44	8.21
20	Spud Chandler S. Chandler	1.62	33.1	6	2	2	.500	4	16	2	1	1	28	6	8	0	9	0	1	0	133	0	4.32	2.43	1.78	0.00	12.0	6.8	1.11	.259	2.16	7.56
21	Scott McGregor S. McGregor	1.63	49.2	6	3	3	.500	6	26	3	2	0	37	9	10	3	8	0	0	2	189	0	4.71	1.45	3.25	0.54	13.8	4.2	0.91	.224	1.81	6.70
22	Jesse Haines J. Haines	1.67	32.1	6	3	1	.750	4	12	2	1	0	24	6	9	3	16	0	1	1	133	1	3.34	4.45	0.75	0.84	9.0	12.0	1.24	.206	2.51	6.68
23	Max Lanier M. Lanier	1.71	31.2	7	2	1	.667	4	25	0	0	0	24	6	10	1	12	0	2	1	132	2	7.11	3.41	2.08	0.28	18.9	9.1	1.14	.245	2.84	6.82
24	Stan Coveleski S. Coveleski	1.74	41.1	5	3	2	.600	5	11	4	1	0	31	8	9	2	7	0	0	0	162	0	2.40	1.52	1.57	0.44	6.8	4.3	0.92	.204	1.96	6.75
25	Lefty Grove L. Grove	1.75	51.1	8	4	2	.667	5	36	4	0	2	46	10	12	0	6	0	3	0	205	0	6.31	1.05	6.00	0.00	17.6	2.9	1.01	.282	2.10	8.06