Since 2004, Shane Bieber has the best K/9 in a season, with 14.20 per nine innings in 2020.

Interpreted as:

highest single season k/9 with a minimum of 1 IP per team game by a player since 2004

	NAME	K/9	SEASON	TM	G	W	L	W%	GS	ERA	SO	CG	SHO	SV	IP	H	ER	R	HR	BB	HBP	GF	IBB	TBF	WP	BB/9	K/BB	HR/9	K%	BB%	WHIP	BABIP	RA	ERA-	FIP	FIP-	H/9	PRAA
1	Shane Bieber S. Bieber	14.20	2020	CLE	12	8	1	.889	12	1.63	122	0	0	0	77.1	46	14	15	7	21	1	0	0	297	5	2.44	5.81	0.81	41.1	7.1	0.87	.267	1.75	37	2.06	46	5.35	20.5
2	Gerrit Cole G. Cole	13.82	2019	HOU	33	20	5	.800	33	2.50	326	0	0	0	212.1	142	59	66	29	48	3	0	0	817	4	2.03	6.79	1.23	39.9	5.9	0.89	.275	2.80	55	2.63	58	6.02	45
3	Jacob deGrom J. deGrom	13.76	2020	NYM	12	4	2	.667	12	2.38	104	0	0	0	68.0	47	18	21	7	18	0	0	0	268	4	2.38	5.78	0.93	38.8	6.7	0.96	.288	2.78	57	2.26	52	6.22	15.9
4	Spencer Strider S. Strider	13.55	2023	ATL	32	19	5	.792	32	3.86	281	0	0	0	186.2	146	80	85	22	58	9	0	1	763	6	2.80	4.84	1.06	36.8	7.6	1.09	.316	4.10	87	2.85	66	7.04	30.3
5	Chris Sale C. Sale	12.93	2017	BOS	32	17	8	.680	32	2.90	308	1	0	0	214.1	165	69	73	24	43	8	0	0	851	3	1.81	7.16	1.01	36.2	5.1	0.97	.301	3.07	63	2.45	56	6.93	45.5
6	Max Scherzer M. Scherzer	12.69	2019	WSH	27	11	7	.611	27	2.92	243	0	0	0	172.1	144	56	59	18	33	7	0	2	693	0	1.72	7.36	0.94	35.1	4.8	1.03	.321	3.08	66	2.44	55	7.52	38.6
7	Corbin Burnes C. Burnes	12.61	2021	MIL	28	11	5	.688	28	2.43	234	0	0	0	167.0	123	45	47	7	34	6	0	0	657	5	1.83	6.88	0.38	35.6	5.2	0.94	.309	2.53	58	1.62	38	6.63	48.9
8	Jose Fernandez J. Fernandez	12.49	2016	MIA	29	16	8	.667	29	2.86	253	0	0	0	182.1	149	58	63	13	55	6	0	6	737	9	2.71	4.60	0.64	34.3	7.5	1.12	.332	3.11	72	2.29	57	7.35	35.4
9	Gerrit Cole G. Cole	12.40	2018	HOU	32	15	5	.750	32	2.88	276	1	1	0	200.1	143	64	68	19	64	7	0	0	799	9	2.88	4.31	0.85	34.5	8.0	1.03	.286	3.05	70	2.70	65	6.42	32.7
10	Trevor Bauer T. Bauer	12.33	2020	CIN	11	5	4	.556	11	1.73	100	2	2	0	73.0	41	14	17	9	17	3	0	1	278	3	2.10	5.88	1.11	36.0	6.1	0.79	.215	2.10	36	2.87	61	5.05	14.1
11	Max Scherzer M. Scherzer	12.30	2020	WSH	12	5	4	.556	12	3.74	92	1	0	0	67.1	70	28	30	10	23	1	0	1	295	6	3.07	4.00	1.34	31.2	7.8	1.38	.355	4.01	83	3.45	76	9.36	8
12	Dylan Cease D. Cease	12.28	2021	CWS	32	13	7	.650	32	3.91	226	1	1	0	165.2	139	72	77	20	68	9	0	0	708	13	3.69	3.32	1.09	31.9	9.6	1.25	.309	4.18	90	3.40	76	7.55	18.9
13	Max Scherzer M. Scherzer	12.24	2018	WSH	33	18	7	.720	33	2.53	300	2	1	0	220.2	150	62	66	23	51	12	0	4	866	4	2.08	5.88	0.94	34.6	5.9	0.91	.265	2.69	62	2.65	64	6.12	36.1
14	Justin Verlander J. Verlander	12.20	2018	HOU	34	16	9	.640	34	2.52	290	1	1	0	214.0	156	60	63	28	37	8	0	0	833	5	1.56	7.84	1.18	34.8	4.4	0.90	.272	2.65	62	2.78	67	6.56	33
15	Robbie Ray R. Ray	12.13	2019	ARI	33	12	8	.600	33	4.34	235	0	0	0	174.1	150	84	91	30	84	5	0	5	747	7	4.34	2.80	1.55	31.5	11.2	1.34	.305	4.70	98	4.28	99	7.74	1
16	Dinelson Lamet D. Lamet	12.13	2020	SDP	12	3	1	.750	12	2.09	93	0	0	0	69.0	39	16	18	5	20	4	0	0	267	1	2.61	4.65	0.65	34.8	7.5	0.86	.234	2.35	49	2.47	56	5.09	15.1
17	Aaron Nola A. Nola	12.11	2020	PHI	12	5	5	.500	12	3.28	96	2	1	0	71.1	54	26	31	9	23	2	0	2	289	1	2.90	4.17	1.14	33.2	8.0	1.08	.283	3.91	73	3.18	70	6.81	10.6
18	Robbie Ray R. Ray	12.11	2017	ARI	28	15	5	.750	28	2.89	218	1	1	0	162.0	116	52	57	23	71	5	0	3	665	8	3.94	3.07	1.28	32.8	10.7	1.15	.267	3.17	63	3.71	85	6.44	11.6
19	Justin Verlander J. Verlander	12.11	2019	HOU	34	21	6	.778	34	2.58	300	2	1	0	223.0	137	64	66	36	42	6	0	0	847	4	1.70	7.14	1.45	35.4	5.0	0.80	.218	2.66	57	3.26	72	5.53	31.5
20	Lucas Giolito L. Giolito	12.07	2020	CWS	12	4	3	.571	12	3.48	97	1	1	0	72.1	47	28	31	8	28	2	0	0	288	3	3.48	3.46	1.00	33.7	9.7	1.04	.255	3.86	78	3.18	69	5.85	11.2
21	Gerrit Cole G. Cole	12.06	2021	NYY	30	16	8	.667	30	3.23	243	2	1	0	181.1	151	65	69	24	41	2	0	0	726	5	2.03	5.93	1.19	33.5	5.6	1.06	.305	3.42	76	2.91	67	7.49	28.1
22	Max Scherzer M. Scherzer	12.02	2017	WSH	31	16	6	.727	31	2.51	268	2	0	0	200.2	126	56	62	22	55	11	0	2	780	4	2.47	4.87	0.99	34.4	7.1	0.90	.245	2.78	57	2.89	66	5.65	33.2
23	Carlos Rodón C. Rodón	11.98	2022	SFG	31	14	8	.636	31	2.88	237	1	0	0	178.0	131	57	59	12	52	3	0	0	710	10	2.63	4.56	0.61	33.4	7.3	1.03	.293	2.98	74	2.25	59	6.62	32.2
24	Yu Darvish Y. Darvish	11.89	2013	TEX	32	13	9	.591	32	2.83	277	0	0	0	209.2	145	66	68	26	80	8	0	1	841	7	3.43	3.46	1.12	32.9	9.5	1.07	.264	2.92	67	3.27	80	6.22	18.5
25	Shohei Ohtani S. Ohtani	11.87	2022	LAA	28	15	9	.625	28	2.33	219	0	0	0	166.0	124	43	45	14	44	2	0	0	660	14	2.39	4.98	0.76	33.2	6.7	1.01	.289	2.44	59	2.40	60	6.72	29.5