Sean O'Sullivan allowed the most earned runs in May 2011, with 30 earned runs.

Interpreted as:

most earned runs allowed by a player in may of 2011

	NAME	ER	MONTH	G	W	L	W%	GS	ERA	SO	CG	SHO	SV	IP	H	R	HR	BB	HBP	GF	IBB	TBF	WP	K/9	BB/9	K/BB	HR/9	K%	BB%	WHIP	BABIP	RA	H/9
1	Sean O'Sullivan S. O'Sullivan	30	May 2011	5	1	3	.250	5	9.10	3	0	0	0	29.2	42	30	8	11	1	0	0	137	0	0.91	3.34	0.27	2.43	2.2	8.0	1.79	.298	9.10	12.74
2	Bronson Arroyo B. Arroyo	28	May 2011	6	0	3	.000	6	7.64	15	0	0	0	33.0	46	29	10	11	0	0	1	152	0	4.09	3.00	1.36	2.73	9.9	7.2	1.73	.310	7.91	12.55
3	Brian Duensing B. Duensing	24	May 2011	6	0	4	.000	5	8.76	19	0	0	0	24.2	34	24	3	13	0	0	2	117	0	6.93	4.74	1.46	1.09	16.2	11.1	1.91	.378	8.76	12.41
4	John Danks J. Danks	24	May 2011	5	0	4	.000	5	6.89	10	1	0	0	31.1	40	25	6	14	1	0	4	141	0	2.87	4.02	0.71	1.72	7.1	9.9	1.72	.309	7.18	11.49
5	Roberto Hernandez R. Hernandez	24	May 2011	6	1	3	.250	6	5.45	27	0	0	0	39.2	40	29	5	9	5	0	0	171	0	6.13	2.04	3.00	1.13	15.8	5.3	1.24	.280	6.58	9.08
6	Brett Myers B. Myers	23	May 2011	5	0	3	.000	5	6.90	24	0	0	0	30.0	40	24	6	13	1	0	2	139	0	7.20	3.90	1.85	1.80	17.3	9.4	1.77	.358	7.20	12.00
7	Wade Davis W. Davis	23	May 2011	6	1	3	.250	6	6.34	16	0	0	0	32.2	44	24	9	18	1	0	0	159	2	4.41	4.96	0.89	2.48	10.1	11.3	1.90	.304	6.61	12.12
8	Chris Carpenter C. Carpenter	22	May 2011	6	1	3	.250	6	5.12	32	1	0	0	38.2	56	26	2	9	1	0	1	178	1	7.45	2.09	3.56	0.47	18.0	5.1	1.68	.403	6.05	13.03
9	Jason Marquis J. Marquis	22	May 2011	6	3	2	.600	6	5.60	14	0	0	0	35.1	44	25	5	12	1	0	1	158	0	3.57	3.06	1.17	1.27	8.9	7.6	1.58	.310	6.37	11.21
10	Jon Lester J. Lester	22	May 2011	6	4	1	.800	6	5.50	39	0	0	0	36.0	41	22	6	17	5	0	0	165	0	9.75	4.25	2.29	1.50	23.6	10.3	1.61	.357	5.50	10.25
11	Chris Volstad C. Volstad	22	May 2011	6	0	3	.000	6	6.32	25	0	0	0	31.1	41	22	5	8	0	0	0	140	0	7.18	2.30	3.13	1.44	17.9	5.7	1.56	.353	6.32	11.78
12	Carl Pavano C. Pavano	22	May 2011	6	0	3	.000	6	5.26	9	0	0	0	37.2	54	26	3	6	0	0	0	170	1	2.15	1.43	1.50	0.72	5.3	3.5	1.59	.336	6.21	12.90
13	Ubaldo Jimenez U. Jimenez	21	May 2011	6	0	4	.000	6	5.45	31	1	0	0	34.2	33	22	1	23	1	0	3	157	5	8.05	5.97	1.35	0.26	19.7	14.6	1.62	.317	5.71	8.57
14	Zack Greinke Z. Greinke	20	May 2011	6	4	1	.800	6	5.29	45	0	0	0	34.0	35	21	5	6	0	0	0	142	0	11.91	1.59	7.50	1.32	31.7	4.2	1.21	.349	5.56	9.26
15	Brandon Morrow B. Morrow	20	May 2011	6	2	2	.500	6	5.51	41	0	0	0	32.2	35	20	0	16	2	0	0	151	2	11.30	4.41	2.56	0.00	27.2	10.6	1.56	.380	5.51	9.64
16	Cliff Lee C. Lee	20	May 2011	7	2	3	.400	7	3.78	51	0	0	0	47.2	52	20	4	15	0	0	0	205	0	9.63	2.83	3.40	0.76	24.9	7.3	1.41	.356	3.78	9.82
17	Brett Anderson B. Anderson	19	May 2011	6	1	3	.250	6	4.42	29	0	0	0	38.2	37	20	3	15	3	0	1	166	0	6.75	3.49	1.93	0.70	17.5	9.0	1.34	.293	4.66	8.61
18	Jason Hammel J. Hammel	19	May 2011	6	0	4	.000	6	4.42	22	0	0	0	38.2	40	22	2	13	1	0	1	169	1	5.12	3.03	1.69	0.47	13.0	7.7	1.37	.290	5.12	9.31
19	Max Scherzer M. Scherzer	19	May 2011	6	2	2	.500	6	4.98	31	0	0	0	34.1	40	20	4	9	1	0	0	151	2	8.13	2.36	3.44	1.05	20.5	6.0	1.43	.340	5.24	10.49
20	R.A. Dickey	19	May 2011	6	1	3	.250	6	4.93	23	0	0	0	34.2	41	20	5	8	3	0	0	152	1	5.97	2.08	2.88	1.30	15.1	5.3	1.41	.319	5.19	10.64
21	Livan Hernandez L. Hernandez	19	May 2011	6	0	4	.000	6	4.54	24	0	0	0	37.2	44	19	6	13	1	0	5	164	1	5.73	3.11	1.85	1.43	14.6	7.9	1.51	.317	4.54	10.51
22	Matt Cain M. Cain	19	May 2011	6	1	3	.250	6	4.27	34	0	0	0	40.0	39	20	3	13	2	0	1	171	0	7.65	2.93	2.62	0.68	19.9	7.6	1.30	.303	4.50	8.78
23	Luke Hochevar L. Hochevar	19	May 2011	6	1	2	.333	6	4.27	14	0	0	0	40.0	37	20	4	15	1	0	1	168	1	3.15	3.38	0.93	0.90	8.3	8.9	1.30	.246	4.50	8.33
24	Ricky Nolasco R. Nolasco	19	May 2011	6	2	1	.667	6	4.31	37	0	0	0	39.2	48	21	4	11	2	0	2	176	0	8.39	2.50	3.36	0.91	21.0	6.3	1.49	.361	4.76	10.89
25	Brad Bergesen B. Bergesen	18	May 2011	5	1	3	.250	5	5.86	15	1	1	0	27.2	33	20	0	9	1	0	1	126	1	4.88	2.93	1.67	0.00	11.9	7.1	1.52	.327	6.51	10.73