highest w% in a single season by a player starting minimum 20 games

Tony Gonsolin has the best win percentage with 20+ starts in a season, at .941 in 2022.

	NAME	W%	GS	G	SEASON	TM	W	L	ERA	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	Tony Gonsolin T. Gonsolin	.941	24	24	2022	LAD	16	1	2.14	119	0	0	0	130.1	79	31	32	11	35	4	0	1	498	5	8.22	2.42	3.40	0.76	23.9	7.0	0.87	.207	2.21	55	3.27	81	5.46	10.8
2	Johnny Allen J. Allen	.938	20	24	1937	CLE	15	1	2.55	87	14	0	0	173.0	157	49	55	4	60	5	4		713	2	4.53	3.12	1.45	0.21	12.2	8.4	1.25	.275	2.86	56	3.46	77	8.17	19.8
3	Greg Maddux G. Maddux	.905	28	28	1995	ATL	19	2	1.63	181	10	3	0	209.2	147	38	39	8	23	4	0	3	785	1	7.77	0.99	7.87	0.34	23.1	2.9	0.81	.244	1.67	39	2.25	52	6.31	46.9
4	Randy Johnson R. Johnson	.900	30	30	1995	SEA	18	2	2.48	294	6	3	0	214.1	159	59	65	12	65	6	0	1	866	5	12.35	2.73	4.52	0.50	33.9	7.5	1.05	.301	2.73	53	2.08	44	6.68	62
5	Ron Guidry R. Guidry	.893	35	35	1978	NYY	25	3	1.74	248	16	9	0	273.2	187	53	61	13	72	1	0	1	1,057	7	8.16	2.37	3.44	0.43	23.5	6.8	0.95	.241	2.01	48	2.18	58	6.15	48.5
6	Lefty Grove L. Grove	.886	30	41	1931	PHA	31	4	2.06	175	27	4	5	288.2	249	66	84	10	62	1	10		1,160	2	5.46	1.93	2.82	0.31	15.1	5.3	1.08	.262	2.62	47	3.01	70	7.76	40.8
7	Aaron Sanchez A. Sanchez	.882	30	30	2016	TOR	15	2	3.00	161	0	0	0	192.0	161	64	69	15	63	5	0	0	790	5	7.55	2.95	2.56	0.70	20.4	8.0	1.17	.267	3.23	71	3.54	83	7.55	14.9
8	Cliff Lee C. Lee	.880	31	31	2008	CLE	22	3	2.54	170	4	2	0	223.1	214	63	68	12	34	5	0	1	891	4	6.85	1.37	5.00	0.48	19.1	3.8	1.11	.301	2.74	59	2.82	67	8.62	35.4
9	Preacher Roe P. Roe	.880	33	34	1951	BKN	22	3	3.04	113	19	2	0	257.2	247	87	91	30	64	0	1		1,031	2	3.95	2.24	1.77	1.05	11.0	6.2	1.21	.263	3.18	76	3.86	94	8.63	6.8
10	Clayton Kershaw C. Kershaw	.875	27	27	2014	LAD	21	3	1.77	239	6	2	0	198.1	139	39	42	9	31	2	0	0	749	7	10.85	1.41	7.71	0.41	31.9	4.1	0.86	.278	1.91	51	1.81	50	6.31	40.5
11	Max Scherzer M. Scherzer	.875	32	32	2013	DET	21	3	2.90	240	0	0	0	214.1	152	69	73	18	56	4	0	0	836	6	10.08	2.35	4.29	0.76	28.7	6.7	0.97	.259	3.07	72	2.74	69	6.38	29.2
12	Tom Seaver T. Seaver	.875	23	23	1981	CIN	14	2	2.54	87	6	1	0	166.1	120	47	51	10	66	3	0	8	671	5	4.71	3.57	1.32	0.54	13.0	9.8	1.12	.218	2.76	72	3.58	104	6.49	-2.2
13	Fred Goldsmith F. Goldsmith	.875	24	26	1880	CWS	21	3	1.75	90	22	4	1	210.1	189	41	80	2	18		1		837	10	3.85	0.77	5.00	0.09	10.8	2.2	0.98		3.42	72	2.06	84	8.09	10.4
14	Joe Wood J. Wood	.872	38	43	1912	BSA	34	5	1.91	258	35	10	1	344.0	267	73	104	2	82	12	5		1,328	7	6.75	2.15	3.15	0.05	19.4	6.2	1.01	.272	2.72	58	2.25	71	6.99	35.1
15	Julio Urías J. Urías	.870	32	32	2021	LAD	20	3	2.96	195	0	0	0	185.2	151	61	67	19	38	7	0	3	745	2	9.45	1.84	5.13	0.92	26.2	5.1	1.02	.272	3.25	73	3.12	73	7.32	23.8
16	Roger Clemens R. Clemens	.870	33	33	2001	NYY	20	3	3.51	213	0	0	0	220.1	205	86	94	19	72	5	0	1	918	14	8.70	2.94	2.96	0.78	23.2	7.8	1.26	.305	3.84	80	3.28	74	8.37	28.1
17	David Cone D. Cone	.870	28	35	1988	NYM	20	3	2.22	213	8	4	0	231.1	178	57	67	10	80	4	0	7	936	10	8.29	3.11	2.66	0.39	22.8	8.5	1.12	.267	2.61	68	2.57	75	6.93	22.5
18	Brad Peacock B. Peacock	.867	21	34	2017	HOU	13	2	3.00	161	0	0	0	132.0	100	44	46	10	57	3	7	0	546	6	10.98	3.89	2.82	0.68	29.5	10.4	1.19	.286	3.14	71	3.06	70	6.82	18.9
19	Zack Greinke Z. Greinke	.864	32	32	2015	LAD	19	3	1.66	200	1	0	0	222.2	148	41	43	14	40	5	0	1	843	7	8.08	1.62	5.00	0.57	23.7	4.7	0.84	.229	1.74	44	2.75	73	5.98	26.2
20	Orel Hershiser O. Hershiser	.864	34	36	1985	LAD	19	3	2.03	157	9	5	0	239.2	179	54	72	8	68	6	1	5	953	5	5.90	2.55	2.31	0.30	16.5	7.1	1.03	.239	2.70	59	2.73	77	6.72	22.1
21	Whitey Ford W. Ford	.862	39	39	1961	NYY	25	4	3.21	209	11	3	0	283.0	242	101	108	23	92	1	0	3	1,159	8	6.65	2.93	2.27	0.73	18.0	7.9	1.18	.263	3.43	85	3.14	82	7.70	22.7
22	Bill Donovan B. Donovan	.862	28	32	1907	DET	25	4	2.19	123	27	3	1	271.0	222	66	96	3	82	8	4		1,073	2	4.08	2.72	1.50	0.10	11.5	7.6	1.12	.256	3.19	84	2.41	98	7.37	2
23	Chris Sale C. Sale	.857	29	29	2024	ATL	18	3	2.38	225	0	0	0	177.2	141	47	48	9	39	8	0	0	702	4	11.40	1.98	5.77	0.46	32.1	5.6	1.01	.314	2.43	57	2.08	52	7.14	38.1
24	Daisuke Matsuzaka D. Matsuzaka	.857	29	29	2008	BOS	18	3	2.90	154	0	0	0	167.2	128	54	58	12	94	7	0	1	716	5	8.27	5.05	1.64	0.64	21.5	13.1	1.32	.258	3.11	64	4.02	96	6.87	2.9
25	Jason Bere J. Bere	.857	24	24	1994	CWS	12	2	3.81	127	0	0	0	141.2	119	60	65	17	80	1	0	0	608	2	8.07	5.08	1.59	1.08	20.9	13.2	1.40	.266	4.13	83	4.61	98	7.56	1.2