Zac Gallen has the worst ERA this season, with an ERA of 5.45.

Interpreted as:

worst rotation era with a minimum of 1 IP per team game by a player this regular season

	NAME	ERA	SEASON	TM	G	W	L	W%	GS	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	Zac Gallen Z. Gallen	5.45	2025	AZ	18	6	9	.400	18	98	0	0	0	104.0	100	63	67	20	42	2	0	1	448	1	8.48	3.63	2.33	1.73	21.9	9.4	1.37	.280	5.80	131	4.97	127	8.65	-12.6
2	Jack Kochanowicz J. Kochanowicz	5.42	2025	LAA	18	3	8	.273	18	62	0	0	0	91.1	100	55	56	16	42	6	0	2	400	3	6.11	4.14	1.48	1.58	15.5	10.5	1.55	.307	5.52	132	5.58	132	9.85	-13.3
3	Brandon Pfaadt B. Pfaadt	5.42	2025	AZ	18	8	6	.571	18	80	0	0	0	91.1	103	55	58	16	23	9	0	1	402	2	7.88	2.27	3.48	1.58	19.9	5.7	1.38	.318	5.72	130	4.66	119	10.15	-7.8
4	Bailey Ober B. Ober	5.28	2025	MIN	17	4	6	.400	17	74	1	0	0	92.0	108	54	55	21	22	4	0	0	406	1	7.24	2.15	3.36	2.05	18.2	5.4	1.41	.305	5.38	131	5.29	129	10.57	-12.2
5	Luis Severino L. Severino	5.09	2025	ATH	18	2	9	.182	18	71	0	0	0	104.1	110	59	64	11	34	8	0	1	462	3	6.12	2.93	2.09	0.95	15.4	7.4	1.38	.293	5.52	127	4.30	105	9.49	-2.4
6	Michael Lorenzen M. Lorenzen	4.95	2025	KCR	17	4	8	.333	17	78	0	0	0	92.2	99	51	53	17	28	2	0	0	400	10	7.58	2.72	2.79	1.65	19.5	7.0	1.37	.298	5.15	117	4.75	116	9.62	-6.8
7	Taj Bradley T. Bradley	4.79	2025	TBR	18	5	6	.455	18	84	0	0	0	97.2	90	52	60	12	37	4	0	0	414	2	7.74	3.41	2.27	1.11	20.3	8.9	1.30	.282	5.53	124	4.22	106	8.29	-2.9
8	JP Sears	4.76	2025	ATH	18	7	7	.500	18	73	0	0	0	92.2	94	49	49	18	24	5	0	0	395	1	7.09	2.33	3.04	1.75	18.5	6.1	1.27	.276	4.76	118	4.97	121	9.13	-9
9	Mitchell Parker M. Parker	4.72	2025	WSH	18	5	9	.357	18	66	0	0	0	97.1	97	51	60	12	37	3	0	0	424	2	6.10	3.42	1.78	1.11	15.6	8.7	1.38	.278	5.55	116	4.56	112	8.97	-5.1
10	Jake Irvin J. Irvin	4.71	2025	WSH	18	7	3	.700	18	75	0	0	0	105.0	102	55	56	20	33	3	0	0	447	1	6.43	2.83	2.27	1.71	16.8	7.4	1.29	.259	4.80	116	5.16	126	8.74	-12.3
11	Kyle Hendricks K. Hendricks	4.68	2025	LAA	17	5	6	.455	17	62	0	0	0	92.1	94	48	51	15	23	4	0	3	391	0	6.04	2.24	2.70	1.46	15.9	5.9	1.27	.275	4.97	114	4.73	112	9.16	-5
12	Chris Paddack C. Paddack	4.64	2025	MIN	18	3	7	.300	18	68	0	0	0	95.0	92	49	53	13	24	3	0	0	400	2	6.44	2.27	2.83	1.23	17.0	6.0	1.22	.271	5.02	115	4.28	105	8.72	-2
13	Dylan Cease D. Cease	4.62	2025	SDP	18	3	8	.273	18	121	0	0	0	97.1	93	50	53	12	36	3	0	1	419	2	11.19	3.33	3.36	1.11	28.9	8.6	1.33	.328	4.90	117	3.40	85	8.60	6.6
14	Erick Fedde E. Fedde	4.56	2025	STL	17	3	8	.273	17	57	1	1	0	92.2	91	47	50	10	41	2	0	1	400	1	5.54	3.98	1.39	0.97	14.3	10.3	1.42	.279	4.86	113	4.65	117	8.84	-7.2
15	Dean Kremer D. Kremer	4.53	2025	BAL	18	7	7	.500	17	81	0	0	0	101.1	108	51	53	14	26	1	0	0	430	5	7.19	2.31	3.12	1.24	18.8	6.0	1.32	.305	4.71	115	4.08	102	9.59	-0.9
16	Jesús Luzardo J. Luzardo	4.44	2025	PHI	18	7	5	.583	18	115	0	0	0	97.1	108	48	52	7	35	1	0	0	423	2	10.63	3.24	3.29	0.65	27.2	8.3	1.47	.381	4.81	108	2.76	67	9.99	14.5
17	Jameson Taillon J. Taillon	4.44	2025	CHC	17	7	6	.538	17	74	0	0	0	95.1	86	47	48	22	20	0	0	0	388	1	6.99	1.89	3.70	2.08	19.1	5.2	1.11	.235	4.53	111	5.16	130	8.12	-13
18	Tomoyuki Sugano T. Sugano	4.44	2025	BAL	17	6	5	.545	17	57	0	0	0	93.1	103	46	47	19	19	4	0	1	397	2	5.50	1.83	3.00	1.83	14.4	4.8	1.31	.282	4.53	113	5.25	131	9.93	-13.1
19	Luis L. Ortiz L. L. Ortiz	4.36	2025	CLE	16	4	9	.308	16	96	0	0	0	88.2	80	43	44	12	42	1	0	0	382	0	9.74	4.26	2.29	1.22	25.1	11.0	1.38	.294	4.47	110	4.13	102	8.12	-0.8
20	Shane Baz S. Baz	4.33	2025	TBR	17	8	3	.727	17	97	0	0	0	97.2	86	47	47	16	36	5	0	0	407	2	8.94	3.32	2.69	1.47	23.8	8.8	1.25	.277	4.33	112	4.48	113	7.92	-5.9
21	Chris Bassitt C. Bassitt	4.32	2025	TOR	18	8	4	.667	18	102	0	0	0	100.0	111	48	50	12	28	8	0	0	440	3	9.18	2.52	3.64	1.08	23.2	6.4	1.39	.341	4.50	109	3.68	90	9.99	4.6
22	Nick Martinez N. Martinez	4.20	2025	CIN	19	6	8	.429	17	71	0	0	0	100.2	97	47	48	14	21	4	0	0	408	5	6.35	1.88	3.38	1.25	17.4	5.1	1.17	.279	4.29	96	4.22	99	8.67	0.9
23	Tanner Bibee T. Bibee	4.20	2025	CLE	17	4	9	.308	17	87	1	0	0	98.2	92	46	49	15	30	7	0	1	415	2	7.94	2.74	2.90	1.37	21.0	7.2	1.24	.279	4.47	105	4.42	109	8.39	-4.1
24	Kevin Gausman K. Gausman	4.18	2025	TOR	17	6	6	.500	17	93	0	0	0	99.0	81	46	47	12	29	3	0	1	401	0	8.45	2.64	3.21	1.09	23.2	7.2	1.11	.261	4.27	105	3.75	92	7.36	3.8
25	Andrew Heaney A. Heaney	4.16	2025	PIT	17	4	7	.364	17	71	0	0	0	93.0	81	43	43	14	31	3	0	0	385	2	6.87	3.00	2.29	1.35	18.4	8.1	1.20	.252	4.16	99	4.61	114	7.84	-5.8