Chad Green pitched the most innings by a relief pitcher in 2021, with 83.2 innings.

	NAME	IP	SEASON	TM	G	W	L	W%	GS	ERA	SO	CG	SHO	SV	H	ER	R	HR	BB	HBP	GF	IBB	TBF	WP	K/9	BB/9	K/BB	HR/9	K%	BB%	WHIP	BABIP	RA	H/9
1	Chad Green C. Green	83.2	2021	NYY	67	10	7	.588	0	3.12	99	0	0	6	57	29	32	14	17	0	15	2	315	5	10.65	1.83	5.82	1.51	31.4	5.4	0.88	.232	3.44	6.13
2	Nabil Crismatt N. Crismatt	81.1	2021	SDP	45	3	1	.750	0	3.76	71	0	0	0	87	34	40	10	24	8	14	2	351	3	7.86	2.66	2.96	1.11	20.2	6.8	1.36	.324	4.43	9.63
3	Tyler Rogers T. Rogers	81.0	2021	SFG	80	7	1	.875	0	2.22	55	0	0	13	74	20	23	5	13	5	18	0	326	0	6.11	1.44	4.23	0.56	16.9	4.0	1.07	.278	2.56	8.22
4	Craig Stammen C. Stammen	80.1	2021	SDP	63	6	3	.667	0	2.80	78	0	0	1	66	25	26	13	10	3	4	0	318	3	8.74	1.12	7.80	1.46	24.5	3.1	0.95	.248	2.91	7.39
5	Giovanny Gallegos G. Gallegos	80.1	2021	STL	73	6	5	.545	0	3.02	95	0	0	14	51	27	28	6	20	6	20	2	310	4	10.64	2.24	4.75	0.67	30.6	6.5	0.88	.246	3.14	5.71
6	Chris Stratton C. Stratton	79.1	2021	PIT	68	7	1	.875	0	3.63	86	0	0	8	70	32	34	9	33	1	18	2	337	3	9.76	3.74	2.61	1.02	25.5	9.8	1.30	.293	3.86	7.94
7	Yusmeiro Petit Y. Petit	78.0	2021	OAK	78	8	3	.727	0	3.92	37	0	0	2	69	34	35	12	12	1	10	1	313	1	4.27	1.38	3.08	1.38	11.8	3.8	1.04	.227	4.04	7.96
8	Bryan Shaw B. Shaw	77.1	2021	CLE	81	6	7	.462	0	3.49	71	0	0	2	69	30	33	10	38	1	10	0	334	6	8.26	4.42	1.87	1.16	21.3	11.4	1.38	.276	3.84	8.03
9	Scott Barlow S. Barlow	74.1	2021	KCR	71	5	3	.625	0	2.42	91	0	0	16	61	20	20	4	28	2	28	2	306	4	11.02	3.39	3.25	0.48	29.7	9.2	1.20	.315	2.42	7.39
10	Héctor Neris H. Neris	74.1	2021	PHI	74	4	7	.364	0	3.63	98	0	0	12	55	30	34	12	32	4	29	3	310	4	11.87	3.87	3.06	1.45	31.6	10.3	1.17	.262	4.12	6.66
11	Lou Trivino L. Trivino	73.2	2021	OAK	71	7	8	.467	0	3.18	67	0	0	22	58	26	32	5	34	4	44	2	310	7	8.19	4.15	1.97	0.61	21.6	11.0	1.25	.265	3.91	7.09
12	Garrett Whitlock G. Whitlock	73.1	2021	BOS	46	8	4	.667	0	1.96	81	0	0	2	64	16	22	6	17	3	11	2	298	3	9.94	2.09	4.76	0.74	27.2	5.7	1.10	.304	2.70	7.85
13	Duane Underwood Jr. D. Underwood Jr.	72.2	2021	PIT	43	2	3	.400	0	4.33	65	0	0	0	77	35	40	9	27	4	6	1	320	3	8.05	3.34	2.41	1.11	20.3	8.4	1.43	.316	4.95	9.54
14	Blake Treinen B. Treinen	72.1	2021	LAD	72	6	5	.545	0	1.99	85	0	0	7	46	16	20	5	25	3	10	1	286	3	10.58	3.11	3.40	0.62	29.7	8.7	0.98	.244	2.49	5.72
15	Alex Reyes A. Reyes	72.1	2021	STL	69	10	8	.556	0	3.24	95	0	0	29	46	26	32	9	52	2	54	1	317	10	11.82	6.47	1.83	1.12	30.0	16.4	1.35	.233	3.98	5.72
16	Adam Cimber A. Cimber	71.2	2021	TOT	72	3	4	.429	0	2.26	51	0	0	1	61	18	24	2	16	7	19	4	286	1	6.40	2.01	3.19	0.25	17.8	5.6	1.07	.281	3.01	7.66
17	Mike Mayers M. Mayers	71.1	2021	LAA	70	5	4	.556	0	3.53	88	0	0	2	65	28	28	11	25	3	9	0	298	0	11.10	3.15	3.52	1.39	29.5	8.4	1.26	.316	3.53	8.20
18	Brent Suter B. Suter	71.0	2021	MIL	60	12	4	.750	0	2.79	67	0	0	1	68	22	31	9	23	1	9	3	301	1	8.49	2.92	2.91	1.14	22.3	7.6	1.28	.294	3.93	8.62
19	Liam Hendriks L. Hendriks	71.0	2021	CWS	69	8	3	.727	0	2.54	113	0	0	38	45	20	23	11	7	1	58	1	267	6	14.32	0.89	16.14	1.39	42.3	2.6	0.73	.252	2.92	5.70
20	Jonathan Loáisiga J. Loáisiga	70.2	2021	NYY	57	9	4	.692	0	2.17	69	0	0	5	56	17	19	3	16	3	8	0	283	4	8.79	2.04	4.31	0.38	24.4	5.7	1.02	.276	2.42	7.13
21	Lucas Luetge L. Luetge	70.1	2021	NYY	56	4	2	.667	0	2.69	77	0	0	1	65	21	29	6	15	3	13	1	293	7	9.85	1.92	5.13	0.77	26.3	5.1	1.14	.307	3.71	8.32
22	Tyler Kinley T. Kinley	70.1	2021	COL	70	3	2	.600	0	4.73	68	0	0	0	59	37	37	12	26	2	7	1	295	4	8.70	3.33	2.62	1.54	23.1	8.8	1.21	.251	4.73	7.55
23	Génesis Cabrera G. Cabrera	70.0	2021	STL	71	4	5	.444	0	3.73	77	0	0	0	52	29	31	3	36	5	5	2	296	9	9.90	4.63	2.14	0.39	26.0	12.2	1.26	.280	3.99	6.69
24	Clay Holmes C. Holmes	70.0	2021	TOT	69	8	4	.667	0	3.60	78	0	0	0	53	28	32	5	29	4	15	2	292	9	10.03	3.73	2.69	0.64	26.7	9.9	1.17	.273	4.11	6.81
25	Raisel Iglesias R. Iglesias	70.0	2021	LAA	65	7	5	.583	0	2.57	103	0	0	34	53	20	25	11	12	1	59	0	273	2	13.24	1.54	8.58	1.41	37.7	4.4	0.93	.288	3.21	6.81