John Coleman has lost the most games in a season, with 48 games in his rookie season in 1883.

Interpreted as:

most losses by a player in a season pitcher

	NAME	L	SEASON	TM	W	L%	G	W%	GS	ERA	SO	CG	SHO	SV	IP	H	ER	R	HR	BB	HBP	GF	TBF	WP	K/9	BB/9	K/BB	HR/9	K%	BB%	WHIP	BABIP	RA	ERA-	FIP	FIP-	H/9	PRAA
1	John Coleman J. Coleman	48	1883	PHN	12	.800	65	.200	61	4.87	159	59	3	0	538.1	772	291	510	17	48		4	2,546	9	2.66	0.80	3.31	0.28	6.2	1.9	1.52		8.53	158	3.34	109	12.91	-19.2
2	Will White W. White	42	1880	CIN	18	.700	62	.300	62	2.14	161	58	3	0	517.1	550	123	323	9	56		0	2,217	35	2.80	0.97	2.88	0.16	7.3	2.5	1.17		5.62	89	2.46	103	9.57	-2.2
3	Larry McKeon L. McKeon	41	1884	IND	18	.695	61	.305	60	3.50	308	59	2	0	512.0	488	199	350	20	94	18	1	2,185	36	5.41	1.65	3.28	0.35	14.1	4.3	1.14	.268	6.15	108	3.24	101	8.58	-1.7
4	George Bradley G. Bradley	40	1879	TRO	13	.755	54	.245	54	2.85	133	53	3	0	487.0	590	154	361	12	26		0	2,170	43	2.46	0.48	5.12	0.22	6.1	1.2	1.26		6.67	115	2.67	108	10.90	-12.6
5	Jim McCormick J. McCormick	40	1879	CLE	20	.667	62	.333	60	2.42	197	59	3	0	546.1	582	147	308	3	74		1	2,325	30	3.25	1.22	2.66	0.05	8.5	3.2	1.20		5.07	101	2.50	104	9.59	-13.4
6	George Cobb G. Cobb	37	1892	BAL	10	.787	53	.213	47	4.86	159	42	0	0	394.1	495	213	333	21	140	19	6	1,836	15	3.63	3.20	1.14	0.48	8.7	7.6	1.61	.317	7.60	145	3.53	105	11.30	-6.1
7	Kid Carsey K. Carsey	37	1891	WSH	14	.725	54	.275	53	4.99	174	46	1	0	415.0	513	230	358	17	161	28	1	1,937	29	3.77	3.49	1.08	0.37	9.0	8.3	1.62	.319	7.76	133	3.59	99	11.13	2.3
8	Henry Porter H. Porter	37	1888	KCC	18	.673	55	.327	54	4.16	145	53	4	0	474.0	527	219	336	16	120	23	1	2,084	24	2.75	2.28	1.21	0.30	7.0	5.8	1.36	.287	6.38	127	3.32	106	10.01	-1.6
9	William Hutchinson W. Hutchinson	36	1892	CHI	36	.500	75	.500	70	2.76	314	67	5	1	622.0	571	191	316	11	190	13	5	2,639	20	4.54	2.75	1.65	0.16	11.9	7.2	1.22	.265	4.57	82	2.63	79	8.26	51.2
10	Stump Wiedman S. Wiedman	36	1886	KCC	12	.750	51	.250	51	4.52	168	48	1	0	427.2	549	215	323	11	112		0	1,924	35	3.54	2.36	1.50	0.23	8.7	5.8	1.55		6.80	129	3.44	97	11.55	11.8
11	Red Donahue R. Donahue	35	1897	STL	10	.778	46	.222	42	6.13	64	38	1	1	348.0	485	237	306	16	106	22	4	1,612	9	1.66	2.74	0.60	0.41	4.0	6.6	1.70	.334	7.91	140	4.65	106	12.54	-8.7
12	Hardie Henderson H. Henderson	35	1885	BAL	25	.583	61	.417	61	3.19	263	59	0	0	539.1	539	191	311	7	117	19	0	2,268	51	4.39	1.95	2.25	0.12	11.6	5.2	1.22	.286	5.19	98	2.83	93	8.99	12.5
13	Fleury Sullivan F. Sullivan	35	1884	PIT	16	.686	51	.314	51	4.20	189	51	2	0	441.0	496	206	328	15	96	20	0	1,967	25	3.86	1.96	1.97	0.31	9.6	4.9	1.34	.292	6.69	131	3.65	115	10.12	-24.7
14	Adonis Terry A. Terry	35	1884	BKN	19	.648	56	.352	55	3.55	230	54	2	0	476.0	486	188	308	10	72	8	1	2,049	33	4.35	1.36	3.19	0.19	11.2	3.5	1.17	.275	5.82	110	3.09	96	9.19	6.4
15	Pud Galvin P. Galvin	35	1880	BUF	20	.636	58	.364	54	2.71	128	46	5	0	458.2	528	138	281	5	32		4	1,969	24	2.51	0.63	4.00	0.10	6.5	1.6	1.22		5.51	112	2.33	96	10.36	7.2
16	Jim Devlin J. Devlin	35	1876	LOU	30	.538	68	.462	68	1.56	122	66	5	0	622.0	566	108	309	3	37		0	2,568	14	1.77	0.54	3.30	0.04	4.8	1.4	0.97		4.47	62	2.08	82	8.19	50.7
17	Amos Rusie A. Rusie	34	1890	NYN	29	.540	67	.460	62	2.56	341	56	4	1	548.2	436	156	300	3	289	26	5	2,379	36	5.59	4.74	1.18	0.05	14.3	12.1	1.32	.252	4.92	73	3.47	92	7.15	17.7
18	Mark Baldwin M. Baldwin	34	1889	COL	27	.557	63	.443	59	3.61	368	54	6	1	513.2	458	206	358	9	274	20	4	2,275	83	6.45	4.80	1.34	0.16	16.2	12.0	1.43	.280	6.27	100	3.52	98	8.02	-3
19	Al Mays A. Mays	34	1887	NYM	17	.667	52	.333	52	4.73	124	50	0	0	441.1	551	232	359	11	136	20	1	2,002	36	2.53	2.77	0.91	0.22	6.2	6.8	1.56	.316	7.32	113	4.10	102	11.24	-5.5
20	Matt Kilroy M. Kilroy	34	1886	BAL	29	.540	68	.460	68	3.37	513	66	5	0	583.0	476	218	350	10	182	19	0	2,469	61	7.92	2.81	2.82	0.15	20.8	7.4	1.13	.267	5.40	100	2.60	77	7.35	47
21	Bob Barr B. Barr	34	1884	TOT	12	.739	48	.261	48	3.94	207	47	2	0	413.0	471	181	327	11	50	18	0	1,853	39	4.51	1.09	4.14	0.24	11.2	2.7	1.26	.294	7.13	125	3.11	100	10.26	-3.1
22	Bobby Mathews B. Mathews	34	1876	NYM	21	.618	56	.382	56	2.86	37	55	2	0	516.0	693	164	395	8	24		0	2,327	3	0.65	0.42	1.54	0.14	1.6	1.0	1.39		6.89	128	2.43	109	12.09	-17.6
23	Jersey Bakley J. Bakley	33	1888	CLE	25	.569	61	.431	61	2.97	212	60	4	0	532.2	518	176	321	14	128	15	0	2,251	40	3.58	2.16	1.66	0.24	9.4	5.7	1.21	.268	5.42	97	2.93	100	8.75	0.1
24	Dupee Shaw D. Shaw	33	1884	TOT	30	.524	67	.476	66	2.30	451	60	5	0	543.1	446	139	281	9	109		1	2,244	24	7.47	1.81	4.14	0.15	20.1	4.9	1.02		4.65	77	2.43	81	7.39	29
25	Hardie Henderson H. Henderson	33	1883	TOT	10	.767	46	.233	43	4.39	147	39	0	0	367.1	409	179	339	4	89		3	1,638	32	3.60	2.18	1.65	0.10	9.0	5.4	1.36		8.31	134	3.32	101	10.02	-1.4