The New York Mets have the best K/9 by a team in a game, with 21.86 per nine innings versus the Rockies on April 17, 2021.

Interpreted as:

highest k/9 as a team in one regular-season game

	TEAM	K/9	DATE	TM		OPP	RESULT	ERA	SO	SHO	SV	IP	H	ER	R	HR	BB	HBP	IBB	TBF	WP	BB/9	K/BB	HR/9	K%	BB%	WHIP	BABIP	RA	H/9
1	Mets	21.86	4/17/2021	NYM	@	COL	W 4-3	0.00	17	0	1	7.0	3	0	3	1	1	0	0	26	0	1.29	17.00	1.29	65.4	3.8	0.57	.286	3.86	3.86
2	Red Sox	20.70	9/25/2016	BOS	@	TBR	W 3-2	1.80	23	0	0	10.0	7	2	2	0	3	1	0	40	0	2.70	7.67	0.00	57.5	7.5	1.00	.538	1.80	6.30
3	Mets	20.25	9/28/2024	NYM	@	MIL	L 0-6	6.75	18	0	0	8.0	9	6	6	0	4	0	0	37	0	4.50	4.50	0.00	48.6	10.8	1.63	.600	6.75	10.13
4	White Sox	20.25	6/18/2023	CWS	@	SEA	L 1-5	5.63	18	0	0	8.0	5	5	5	0	4	0	0	33	0	4.50	4.50	0.00	54.5	12.1	1.13	.455	5.63	5.63
5	Packers	20.25	10/4/1914	KCP	@	IND	L 0-4	0.00	9	0	0	4.0	2	0	4	0	1	1		18	0	2.25	9.00	0.00	50.0	5.6	0.75	.286	9.00	4.50
6	Mets	20.00	9/18/2022	NYM	vs	PIT	W 7-3	3.00	20	0	0	9.0	5	3	3	1	0	1	0	33	0	0.00		1.00	60.6	0.0	0.56	.364	3.00	5.00
7	Astros	20.00	7/3/2022	HOU	vs	LAA	W 4-2	2.00	20	0	0	9.0	4	2	2	1	5	0	0	35	0	5.00	4.00	1.00	57.1	14.3	1.00	.333	2.00	4.00
8	White Sox	20.00	4/28/2019	CWS	vs	DET	W 4-1	0.00	20	0	1	9.0	2	0	1	0	4	0	0	33	0	4.00	5.00	0.00	60.6	12.1	0.67	.222	1.00	2.00
9	Red Sox	20.00	5/25/2017	BOS	vs	TEX	W 6-2	2.00	20	0	0	9.0	4	2	2	1	1	0	0	33	1	1.00	20.00	1.00	60.6	3.0	0.56	.273	2.00	4.00
10	Nationals	20.00	5/11/2016	WSH	vs	DET	W 3-2	2.00	20	0	0	9.0	6	2	2	2	0	0	0	33	0	0.00		2.00	60.6	0.0	0.67	.364	2.00	6.00
11	Angels	20.00	9/25/2012	LAA	vs	SEA	W 5-4	4.00	20	0	1	9.0	11	4	4	2	2	0	0	40	1	2.00	10.00	2.00	50.0	5.0	1.44	.563	4.00	11.00
12	Cubs	20.00	5/6/1998	CHC	vs	HOU	W 2-0	0.00	20	1	0	9.0	1	0	0	0	0	1	0	29	0	0.00		0.00	69.0	0.0	0.11	.125	0.00	1.00
13	Red Sox	20.00	9/18/1996	BOS	@	DET	W 4-0	0.00	20	1	0	9.0	5	0	0	0	0	0	0	32	1	0.00		0.00	62.5	0.0	0.56	.417	0.00	5.00
14	Red Sox	20.00	4/29/1986	BOS	vs	SEA	W 3-1	1.00	20	0	0	9.0	3	1	1	1	0	0	0	30	0	0.00		1.00	66.7	0.0	0.33	.222	1.00	3.00
15	Red Sox	19.64	5/14/2019	BOS	vs	COL	L 4-5	4.09	24	0	0	11.0	6	5	5	2	2	0	0	41	0	1.64	12.00	1.64	58.5	4.9	0.73	.308	4.09	4.91
16	Dodgers	19.50	6/2/2017	LAD	@	MIL	W 2-1	0.75	26	0	0	12.0	5	1	1	1	2	1	1	45	0	1.50	13.00	0.75	57.8	4.4	0.58	.267	0.75	3.75
17	Athletics	19.50	4/9/1971	OAK	vs	KCR	W 5-0	0.00	13	1	0	6.0	3	0	0	0	2	0	0	24	0	3.00	6.50	0.00	54.2	8.3	0.83	.333	0.00	4.50
18	Mariners	19.44	9/27/1992	SEA	@	TEX	L 2-3	2.16	18	0	0	8.1	7	2	3	0	5	0	1	38	0	5.40	3.60	0.00	47.4	13.2	1.44	.467	3.24	7.56
19	Giants	19.13	5/5/2024	SFG	@	PHI	L 4-5	4.50	17	0	0	8.0	10	4	5	1	2	0	0	37	0	2.25	8.50	1.13	45.9	5.4	1.50	.529	5.63	11.25
20	Astros	19.13	7/13/2022	HOU	@	LAA	L 1-7	7.88	17	0	0	8.0	12	7	7	0	6	0	0	42	1	6.75	2.83	0.00	40.5	14.3	2.25	.632	7.88	13.50
21	Padres	19.13	7/1/2022	SDP	@	LAD	L 1-5	5.63	17	0	0	8.0	10	5	5	2	4	0	0	38	1	4.50	4.25	2.25	44.7	10.5	1.75	.533	5.63	11.25
22	White Sox	19.13	7/25/2017	CWS	@	CHC	L 2-7	7.88	17	0	0	8.0	10	7	7	1	9	1	1	44	0	10.13	1.89	1.13	38.6	20.5	2.38	.563	7.88	11.25
23	Cardinals	19.13	4/15/2017	STL	@	NYY	L 2-3	2.25	17	0	0	8.0	5	2	3	0	8	0	0	39	2	9.00	2.13	0.00	43.6	20.5	1.63	.357	3.38	5.63
24	Diamondbacks	19.13	6/30/1999	ARI	@	CIN	L 0-2	2.25	17	0	0	8.0	7	2	2	1	0	0	0	30	0	0.00		1.13	56.7	0.0	0.88	.500	2.25	7.88
25	Orioles	19.13	7/5/1997	BAL	@	DET	L 5-6	6.75	17	0	0	8.0	8	6	6	2	5	0	1	35	2	5.63	3.40	2.25	48.6	14.3	1.63	.545	6.75	9.00