MLB · Player

William Kempner

#71 P · B/T: R/R · 6' 0", 222 lb · Age 25 · San Jose, CA, USA · MLB debut 2026 · Draft: 2022 Rd 3 #106 (SF) — Gonzaga · Miami Marlins

Compare

Career Graph

Season	Team	W	L	SV	BS	G	GS	QS	IP	IP/G	SO	K/9	BB/9	ERA	FIP	WAR
2026	MIA	1	0	0	0	9	0	0	12.1	1.4	14	10.2	2.9	2.92	3.34	0.1
Career		1	0	0	0	9	0	0	12.1	1.4	14	10.2	2.9	2.92	—	0.1

Season	Team	W	L	SV	BS	G	GS	QS	IP	IP/G	SO	K/9	BB/9	ERA
Triple-A (AAA)
2025	JAX	3	0	1	0	13	0	0	17.0	1.3	25	13.2	7.9	2.65
2026	JAX	0	3	6	1	24	0	—	31.2	1.3	52	14.8	6.0	3.98
AAA Total		3	3	7	1	37	0	0	48.2	1.3	77	14.2	6.7	3.51
Double-A (AA)
2023	RIC	0	0	0	0	1	0	—	1.2	1.7	2	10.8	10.8	5.40
2025	PNS	3	1	0	0	16	0	0	24.0	1.5	31	11.6	5.6	1.13
AA Total		3	1	0	0	17	0	0	25.2	1.5	33	11.6	6.0	1.40
High-A (A+)
2023	EUG	3	2	0	3	23	0	—	34.0	1.5	47	12.4	3.4	2.91
2025	BEL	1	2	6	0	19	0	—	26.2	1.4	39	13.2	3.4	3.04
A+ Total		4	4	6	3	42	0	—	60.2	1.4	86	12.8	3.4	2.97
Single-A (A)
2022	SJ	0	0	0	0	3	2	—	5.2	1.9	6	9.5	6.4	6.35
2023	SJ	1	3	1	0	14	5	—	27.0	1.9	29	9.7	5.0	4.67
A Total		1	3	1	0	17	7	—	32.2	1.9	35	9.6	5.2	4.96
Rookie (Rk)
2022	A-GIA	1	0	0	0	2	0	—	3.1	1.7	5	13.5	5.4	2.70
Rk Total		1	0	0	0	2	0	—	3.1	1.7	5	13.5	5.4	2.70
Minors Total		12	11	14	4	115	7	0	171.0	1.5	236	12.4	5.1	3.26

Season	Team	G	PA	AB	R	H	2B	3B	HR	RBI	SB	BB	SO	BB%	K%	AVG	OBP	SLG	OPS	wOBA	wRC+	WAR
2026	MIA	9	0	0	0	0	0	0	0	0	0	0	0	—	—	.000	.000	.000	.000	—	—	0.0
Career		9	0	0	0	0	0	0	0	0	0	0	0	—	—	—	—	—	—	—	—	0.0

Season	Team	Pos	G	Inn	PO	A	E	FPCT
2026	MIA	P	9	12.1	1	0	0	1.000
Career		P	9	12.1	1	0	0	1.000

Season	Team	Pos	G	Inn	PO	A	E	FPCT
Triple-A (AAA)
2025	JAX	P	13	17.0	1	2	0	1.000
2026	JAX	P	24	31.2	1	0	0	1.000
AAA Total		—	37	48.2	2	2	0	1.000
Double-A (AA)
2023	RIC	P	1	1.2	0	0	0	.000
2025	PNS	P	16	24.0	2	2	0	1.000
AA Total		—	17	25.2	2	2	0	1.000
High-A (A+)
2023	EUG	P	23	34.0	3	1	1	.800
2025	BEL	P	19	26.2	0	0	2	.000
A+ Total		—	42	60.2	3	1	3	.571
Single-A (A)
2022	SJ	P	3	5.2	1	0	0	1.000
2023	SJ	P	14	27.0	1	8	0	1.000
A Total		—	17	32.2	2	8	0	1.000
Rookie (Rk)
2022	A-GIA	P	2	3.1	0	0	0	.000
Rk Total		—	2	3.1	0	0	0	—
Minors Total		—	115	171.0	9	13	3	.880

1 W · 3.26 ERA · 46 SO

2 W · 3.83 ERA · 39 SO

1 W · 2.08 ERA · 29 SO

2 W · 3.13 ERA · 34 SO

4 W · 2.54 ERA · 53 SO