Satchel Paige and Charley O'Leary are tied for the oldest in a season. They were 58 years old.

Interpreted as:

the oldest starting in a regular season player

	NAME	AGE	GS	SEASON	TM	G	W	L	W%	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	Satchel Paige S. Paige	58	1	1965	KCA	1	0	0		0.00	1	0	0	0	3.0	1	0	0	0	0	0	0	0	10	0	3.00	0.00		0.00	10.0	0.0	0.33	.111	0.00	0	1.85	51	3.00	0.6
2	Charley O'Leary C. O'Leary	58		1934	SLA
3	Nick Altrock N. Altrock	56		1933	WSH
4	Minnie Minoso M. Minoso	54		1980	CWS
5	Nick Altrock N. Altrock	54		1931	WSH
6	Jim O'Rourke J. O'Rourke	53		1904	NYG
7	Nick Altrock N. Altrock	52		1929	WSH
8	Minnie Minoso M. Minoso	50		1976	CWS
9	Jack Quinn J. Quinn	50	0	1933	CIN	14	0	1	.000	4.02	3	0	0	1	15.2	20	7	9	0	5	0	9		71	0	1.72	2.87	0.60	0.00	4.2	7.0	1.60	.317	5.17	123	3.37	97	11.49	0.2
10	Jamie Moyer J. Moyer	49	10	2012	COL	10	2	5	.286	5.70	36	0	0	0	53.2	75	34	40	11	18	2	0	2	254	0	6.04	3.02	2.00	1.84	14.2	7.1	1.73	.342	6.71	124	5.53	131	12.58	-7.1
11	Jack Quinn J. Quinn	49	0	1932	BKN	42	3	7	.300	3.30	28	0	0	9	87.1	102	32	36	1	24	1	32		378	7	2.89	2.47	1.17	0.10	7.4	6.3	1.44	.312	3.71	87	3.38	87	10.51	5
12	Jimmy Austin J. Austin	49		1929	SLA
13	Hughie Jennings H. Jennings	49		1918	DET
14	Arlie Latham A. Latham	49		1909	NYG
15	Julio Franco J. Franco	48		2007	TOT
16	Phil Niekro P. Niekro	48	26	1987	TOT	26	7	13	.350	6.30	64	2	0	0	138.2	163	97	99	22	66	4	0	1	637	10	4.15	4.28	0.97	1.43	10.0	10.4	1.65	.293	6.43	140	5.51	124	10.58	-16.4
17	Hoyt Wilhelm H. Wilhelm	48	0	1972	LAD	16	0	1	.000	4.62	9	0	0	1	25.1	20	13	16	0	15	0	9	0	112	4	3.20	5.33	0.60	0.00	8.0	13.4	1.38	.227	5.68	142	3.46	111	7.11	-1.1
18	Jack Quinn J. Quinn	48	1	1931	BKN	39	5	4	.556	2.66	25	0	0	13	64.1	65	19	28	1	24	1	29		279	1	3.50	3.36	1.04	0.14	9.0	8.6	1.38	.281	3.92	70	3.70	94	9.09	1.5
19	Gabby Street G. Street	48		1931	SLN
20	Deacon McGuire D. McGuire	48		1912	DET
21	Jamie Moyer J. Moyer	47	19	2010	PHI	19	9	9	.500	4.84	63	2	1	0	111.2	103	60	64	20	20	6	0	0	460	0	5.08	1.61	3.15	1.61	13.7	4.3	1.10	.236	5.16	120	4.97	125	8.30	-12.2
22	Julio Franco J. Franco	47		2006	NYM
23	Phil Niekro P. Niekro	47	32	1986	CLE	34	11	11	.500	4.32	81	5	0	0	210.1	241	101	126	24	95	6	1	1	951	9	3.47	4.06	0.85	1.03	8.5	10.0	1.60	.291	5.39	102	4.91	118	10.31	-17.8
24	Hoyt Wilhelm H. Wilhelm	47	0	1971	TOT	12	0	1	.000	2.70	16	0	0	3	20.0	12	6	7	3	5	0	7	0	72	0	7.20	2.25	3.20	1.35	22.2	6.9	0.85	.188	3.15	76	3.55	105	5.40	-0.4
25	Jack Quinn J. Quinn	47	6	1930	PHA	35	9	7	.563	4.42	28	0	0	6	89.2	109	44	51	6	22	1	17		397	1	2.81	2.21	1.27	0.60	7.1	5.5	1.46	.303	5.12	92	4.52	93	10.94	3.4