Bert Blyleven has started the most career games by a pitcher younger than 30, with 382 starts.

Interpreted as:

most regular-season games started by a player before age 30

	NAME	GS	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	H/9
1	Bert Blyleven B. Blyleven	382	387	156	141	.525	2.96	2,250	150	41	0	2841.1	2,554	933	1,051	206	770	70	3	48	11,630	63	7.13	2.44	2.92	0.65	19.3	6.6	1.17	.282	3.33	8.09
2	Catfish Hunter C. Hunter	379	402	184	127	.592	3.06	1,696	146	38	1	2784.1	2,327	947	1,054	286	770	41	5	49	11,277	37	5.48	2.49	2.20	0.92	15.0	6.8	1.11	.241	3.41	7.52
3	Walter Johnson W. Johnson	369	452	249	155	.616	0.93	2,245	321	69	17	3366.1	2,574		924	28	683	127	78			114	6.00	1.83	3.29	0.07		5.2	0.97	.253	2.47	6.88
4	Don Drysdale D. Drysdale	366	419	170	129	.569	3.03	2,038	139	34	6	2727.0	2,428	918	1,052	232	709	127	34	91	11,232	67	6.73	2.34	2.87	0.77	18.1	6.3	1.15	.270	3.47	8.01
5	Hal Newhouser H. Newhouser	342	419	188	134	.584	2.96	1,691	201	33	18	2717.1	2,405	894	1,057	111	1,157	15	61		11,483	59	5.60	3.83	1.46	0.37	14.7	10.1	1.31	.270	3.50	7.97
6	Ken Holtzman K. Holtzman	336	348	151	124	.549	3.28	1,438	108	26	1	2360.1	2,202	861	992	197	719	40	4	54	9,848	74	5.48	2.74	2.00	0.75	14.6	7.3	1.24	.269	3.78	8.40
7	Felix Hernandez F. Hernandez	335	335	143	102	.584	3.11	2,148	25	11	0	2268.1	2,020	784	873	184	635	72	0	16	9,278	126	8.52	2.52	3.38	0.73	23.2	6.8	1.17	.294	3.46	8.01
8	Milt Pappas M. Pappas	331	373	153	113	.575	3.35	1,343	96	32	4	2276.2	2,085	847	933	203	650	50	28	52	9,378	79	5.31	2.57	2.07	0.80	14.3	6.9	1.20	.264	3.69	8.24
9	Joe Coleman J. Coleman	328	385	133	131	.504	3.72	1,627	92	18	5	2336.2	2,191	966	1,095	214	909	85	27	59	9,954	102	6.27	3.50	1.79	0.82	16.3	9.1	1.33	.278	4.22	8.44
10	Fernando Valenzuela F. Valenzuela	320	331	141	116	.549	3.31	1,759	107	29	2	2348.2	2,099	864	981	152	915	16	5	58	9,857	94	6.74	3.51	1.92	0.58	17.8	9.3	1.28	.278	3.76	8.04
11	Larry Dierker L. Dierker	320	345	137	117	.539	3.28	1,487	106	25	1	2294.0	2,089	837	927	177	695	48	9	45	9,489	101	5.83	2.73	2.14	0.69	15.7	7.3	1.21	.270	3.64	8.20
12	Vida Blue V. Blue	319	330	150	104	.591	3.09	1,570	121	32	2	2353.2	2,038	808	918	169	762	18	2	39	9,642	67	6.00	2.91	2.06	0.65	16.3	7.9	1.19	.262	3.51	7.79
13	Robin Roberts R. Roberts	319	358	179	119	.601	3.16	1,301	202	28	21	2599.1	2,453	914	1,014	245	530	30	33		10,584	22	4.50	1.84	2.45	0.85	12.3	5.0	1.15	.260	3.51	8.49
14	Don Sutton D. Sutton	318	332	139	113	.552	3.04	1,738	99	36	3	2290.0	1,968	774	854	170	591	44	9	55	9,334	58	6.83	2.32	2.94	0.67	18.6	6.3	1.12	.265	3.36	7.73
15	Sam McDowell S. McDowell	318	362	130	117	.526	3.10	2,271	101	22	11	2259.1	1,747	778	887	149	1,152	58	25	66	9,551	124	9.05	4.59	1.97	0.59	23.8	12.1	1.28	.270	3.53	6.96
16	Dave McNally D. McNally	309	335	148	86	.632	3.13	1,279	90	25	1	2127.2	1,893	739	808	187	628	55	6	38	8,714	47	5.41	2.66	2.04	0.79	14.7	7.2	1.18	.260	3.42	8.01
17	Dick Ellsworth D. Ellsworth	309	353	112	133	.457	3.71	1,108	87	9	2	2081.1	2,192	857	997	189	572	42	16	69	8,838	70	4.79	2.47	1.94	0.82	12.5	6.5	1.33	.289	4.31	9.48
18	CC Sabathia	308	308	148	84	.638	3.59	1,700	30	11	0	2027.1	1,854	808	879	180	635	63	0	25	8,391	42	7.55	2.82	2.68	0.80	20.3	7.6	1.23	.288	3.90	8.23
19	Rick Porcello R. Porcello	307	311	135	106	.560	4.26	1,364	10	3	0	1863.0	1,998	881	967	224	429	76	2	15	7,883	64	6.59	2.07	3.18	1.08	17.3	5.4	1.30	.306	4.67	9.65
20	Dwight Gooden D. Gooden	303	305	157	85	.649	3.10	1,875	67	23	1	2169.2	1,898	747	823	123	651	41	1	31	8,898	47	7.78	2.70	2.88	0.51	21.1	7.3	1.17	.286	3.41	7.87
21	Dennis Eckersley D. Eckersley	302	318	134	110	.549	3.64	1,373	93	18	3	2125.2	2,030	859	931	232	562	50	8	57	8,872	22	5.81	2.38	2.44	0.98	15.5	6.3	1.22	.270	3.94	8.59
22	Bob Feller B. Feller	301	348	177	98	.644	2.99	2,000	198	34	20	2471.0	1,961	822	911	107	1,246	37	36		10,403	59	7.28	4.54	1.61	0.39	19.2	12.0	1.30	.264	3.32	7.14
23	Greg Maddux G. Maddux	300	304	151	94	.616	2.88	1,488	70	20	0	2142.1	1,896	685	791	109	563	61	3	84	8,747	37	6.25	2.37	2.64	0.46	17.0	6.4	1.15	.274	3.32	7.97
24	Bob Friend B. Friend	299	380	121	139	.465	3.76	1,085	105	20	7	2251.1	2,348	941	1,083	194	630	23	39	60	9,545	33	4.34	2.52	1.72	0.78	11.4	6.6	1.32	.283	4.33	9.39
25	Steve Carlton S. Carlton	292	310	133	105	.559	3.05	1,724	131	28	1	2196.0	1,968	743	844	156	785	26	7	68	9,147	78	7.07	3.22	2.20	0.64	18.8	8.6	1.25	.281	3.46	8.07