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
Career Graph
Pitching
| Season | Team | W | L | SV | G | GS | QS | IP | IP/G | SO | K/9 | BB/9 | ERA | FIP | WAR |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 2026 | MIA | 1 | 0 | 0 | 9 | 0 | 0 | 12.1 | 1.4 | 14 | 10.2 | 2.9 | 2.92 | 3.36 | 0.1 |
| 2026 pace | 2 | 0 | 0 | 14 | 0 | 18.2 | 21 | ||||||||
| Career | 1 | 0 | 0 | 9 | 0 | 0 | 12.1 | 1.4 | 14 | 10.2 | 2.9 | 2.92 | — | — |
| Season | Team | W | L | SV | G | GS | QS | IP | IP/G | SO | K/9 | BB/9 | ERA | FIP | WAR |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Triple-A (AAA) | |||||||||||||||
| 2025 | JAX | 3 | 0 | 1 | 13 | 0 | — | 17.0 | 1.3 | 25 | 13.2 | 7.9 | 2.65 | — | — |
| 2026 | JAX | 0 | 3 | 6 | 24 | 0 | — | 31.2 | 1.3 | 52 | 14.8 | 6.0 | 3.98 | — | — |
| AAA Total | 3 | 3 | 7 | 37 | 0 | — | 48.2 | 1.3 | 77 | 14.2 | 6.7 | 3.51 | — | — | |
| Double-A (AA) | |||||||||||||||
| 2023 | RIC | 0 | 0 | 0 | 1 | 0 | — | 1.2 | 1.7 | 2 | 10.8 | 10.8 | 5.40 | — | — |
| 2025 | PNS | 3 | 1 | 0 | 16 | 0 | — | 24.0 | 1.5 | 31 | 11.6 | 5.6 | 1.13 | — | — |
| AA Total | 3 | 1 | 0 | 17 | 0 | — | 25.2 | 1.5 | 33 | 11.6 | 6.0 | 1.40 | — | — | |
| High-A (A+) | |||||||||||||||
| 2023 | EUG | 3 | 2 | 0 | 23 | 0 | — | 34.0 | 1.5 | 47 | 12.4 | 3.4 | 2.91 | — | — |
| 2025 | BEL | 1 | 2 | 6 | 19 | 0 | — | 26.2 | 1.4 | 39 | 13.2 | 3.4 | 3.04 | — | — |
| A+ Total | 4 | 4 | 6 | 42 | 0 | — | 60.2 | 1.4 | 86 | 12.8 | 3.4 | 2.97 | — | — | |
| Single-A (A) | |||||||||||||||
| 2022 | SJ | 0 | 0 | 0 | 3 | 2 | — | 5.2 | 1.9 | 6 | 9.5 | 6.4 | 6.35 | — | — |
| 2023 | SJ | 1 | 3 | 1 | 14 | 5 | — | 27.0 | 1.9 | 29 | 9.7 | 5.0 | 4.67 | — | — |
| A Total | 1 | 3 | 1 | 17 | 7 | — | 32.2 | 1.9 | 35 | 9.6 | 5.2 | 4.96 | — | — | |
| Rookie (Rk) | |||||||||||||||
| 2022 | A-GIA | 1 | 0 | 0 | 2 | 0 | — | 3.1 | 1.7 | 5 | 13.5 | 5.4 | 2.70 | — | — |
| Rk Total | 1 | 0 | 0 | 2 | 0 | — | 3.1 | 1.7 | 5 | 13.5 | 5.4 | 2.70 | — | — | |
| Minors Total | 12 | 11 | 14 | 115 | 7 | — | 171.0 | 1.5 | 236 | 12.4 | 5.1 | 3.26 | — | — | |
Batting
| 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 |
| 2026 pace | 14 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | ||||||||||
| Career | 9 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | — | — | — | — | — | — | — | — | — |
Fielding
| 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 | |
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