William Kempner

William Kempner

25-Year-Old PitcherRP
Miami Marlins AAA
2026 Fantasy Outlook
There was no outlook written for William Kempner in 2026. Check out the latest news below for more on his current fantasy value.
Signed a one-year contract with the Marlins in March of 2026.
Returns to Triple-A
PMiami Marlins  AAA
June 16, 2026
Kempner was optioned to Triple-A Jacksonville on Tuesday.
Analysis
The right-hander fired 2.1 scoreless innings Monday against the Phillies and is being sent down Tuesday in favor of a fresh bullpen arm (Dax Fulton). Kempner has given up just three hits with a 10:2 K:BB across nine scoreless frames in the majors this season, so it should only be a matter of time before he gets another look with the big club.
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Pitching Stats
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2026 MLB Game Log
2026
2026 MLB Game Log
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Scoring
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Minor League Game Log
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Pitching Appearances Breakdown
Average Pitch Count
22
Last 10 Games
22
Last 5 Games
24
How many pitches does William Kempner generally throw?
 
1-10
 
11-20
 
21-30
 
31-40
 
41-50
 
51-60
 
61-70
 
71-80
 
81-90
 
91-100
 
101-110
 
111-120
 
121+
 
1-10
 
11-20
 
21-30
 
31-40
 
41-50
 
51-60
 
61-70
 
71-80
 
81-90
 
91-100
 
101-110
 
111-120
 
121+
 
1-10
 
11-20
 
21-30
 
31-40
 
41-50
 
51-60
 
61-70
 
71-80
 
81-90
 
91-100
 
101-110
 
111-120
 
121+
What part of the game does William Kempner generally pitch?
 
 
 
1st
 
 
 
2nd
 
 
 
3rd
 
 
 
4th
 
 
 
5th
 
 
 
6th
 
 
 
7th
 
 
 
8th
 
 
 
9th
 
Extra
 
 
 
1st
 
 
 
2nd
 
 
 
3rd
 
 
 
4th
 
 
 
5th
 
 
 
6th
 
 
 
7th
 
 
 
8th
 
 
 
9th
 
Extra
 
 
 
1st
 
 
 
2nd
 
 
 
3rd
 
 
 
4th
 
 
 
5th
 
 
 
6th
 
 
 
7th
 
 
 
8th
 
 
 
9th
 
Extra
% Games Reaching Innings Threshold
% Games By Number of Innings Pitched
Left/Right Pitching Splits
Since 2024
 
 
-100%
BAA vs LHP
2026
 
 
-100%
BAA vs LHP
2025
No Stats
2024
No Stats
BAA Batters K BB H 2B 3B HR
Since 2024vs Left .000 18 9 1 0 0 0 0
Since 2024vs Right .231 15 1 1 3 0 0 0
2026vs Left .000 18 9 1 0 0 0 0
2026vs Right .231 15 1 1 3 0 0 0
2025vs Left 0 0 0 0 0 0 0 0
2025vs Right 0 0 0 0 0 0 0 0
2024vs Left 0 0 0 0 0 0 0 0
2024vs Right 0 0 0 0 0 0 0 0
Home/Away Pitching Splits
Since 2024
No Stats
2026
No Stats
2025
No Stats
2024
No Stats
ERA WHIP IP W L SV K/9 BB/9 HR/9
Since 2024Home 0.00 0.69 4.1 1 0 0 10.4 4.2 0.0
Since 2024Away 0.00 0.43 4.2 0 0 0 9.6 0.0 0.0
2026Home 0.00 0.69 4.1 1 0 0 10.4 4.2 0.0
2026Away 0.00 0.43 4.2 0 0 0 9.6 0.0 0.0
2025Home 0 0 0 0 0 0 0 0 0
2025Away 0 0 0 0 0 0 0 0 0
2024Home 0 0 0 0 0 0 0 0 0
2024Away 0 0 0 0 0 0 0 0 0
Minor League Left/Right Pitching Splits (AAA)
Since 2024
 
 
-21%
BAA vs LHP
2026
 
 
-1%
BAA vs RHP
2025
 
 
-48%
BAA vs LHP
2024
No Stats
BAA Batters K BB H 2B 3B HR
Since 2024vs Left .139 92 38 14 10 1 0 3
Since 2024vs Right .176 94 33 17 13 1 0 2
2026vs Left .171 51 23 6 7 1 0 2
2026vs Right .170 59 23 10 8 1 0 1
2025vs Left .097 41 15 8 3 0 0 1
2025vs Right .185 35 10 7 5 0 0 1
2024vs Left 0 0 0 0 0 0 0 0
2024vs Right 0 0 0 0 0 0 0 0
Stat Review
How does William Kempner compare to other relievers?
This section compares his stats with all relief pitcher seasons from the previous three seasons (minimum 30 innings)*. The bar represents the player's percentile rank. For example, if the bar is halfway across, then the player falls into the 50th percentile for that stat and it would be considered average.

* Exit Velocity, Barrels/BBE %, Balls Hit 95+ MPH %, and Spin Rate are benchmarked against 2019 data (min 30 IP). See here for more exit velocity/barrels stats plus an explanation of current limitations with that data set.
  • K/BB
    Strikeout to walk ratio.
  • K/9
    Average strikeouts per nine innings.
  • BB/9
    Average walks per nine innings.
  • HR/9
    Average home runs allowed per nine innings.
  • Fastball
    Average fastball velocity.
  • ERA
    Earned run average. The average earned runs allowed per nine innings.
  • WHIP
    Walks plus hits per inning pitched.
  • BABIP
    Batting average on balls in play. Measures how many balls in play against a pitcher go for hits.
  • GB/FB
    Groundball to flyball ratio. The higher the number, the more likely a pitcher is to induce groundballs.
  • Left On Base
    The percentage of base runners that a pitcher strands on base over the course of a season.
  • Exit Velocity
    The speed of the baseball as it comes off the bat, immediately after a batter makes contact.
  • Barrels/BBE
    The percentage of batted ball events resulting in a Barrel. A Barrel is a batted ball with similar exit velocity and launch angle to past ones that led to a minimum .500 batting average and 1.500 slugging percentage.
  • Spin Rate
    Spin Rate is the rate of spin on a baseball after it is released. It is measured in revolutions per minute (rpm).
  • Balls Hit 95+ MPH
    The percentage of batted balls hit that met or exceeded the 95 MPH threshold.
  • Swinging Strike
    The percentage of pitches that result in a swing and a miss.
K/BB
5.00
 
K/9
10.0
 
BB/9
2.0
 
HR/9
0.0
 
Fastball
95.3 mph
 
ERA
0.00
 
WHIP
0.56
 
BABIP
.163
 
GB/FB
0.86
 
Left On Base
100.0%
 
Exit Velocity
79.6 mph
 
Barrels/BBE
0.0%
 
Spin Rate
2566 rpm
 
Balls Hit 95+ MPH
8.6%
 
Swinging Strike
16.1%
 
Advanced Pitching Stats
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Defensive Stats
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Stats Vs Today's Lineup
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Recent RotoWire Articles Featuring William Kempner See More
Recent RotoWire Articles Featuring William Kempner See More
More Fantasy News
Nabs first big-league win
PMiami Marlins  AAA
June 11, 2026
Kempner (1-0) picked up the win Wednesday, walking two and striking out three over two scoreless, no-hit innings of relief in a victory over the Diamondbacks.
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Recalled from Triple-A
PMiami Marlins  AAA
May 30, 2026
The Marlins recalled Kempner from Triple-A Jacksonville on Saturday.
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Sent back to minors
PMiami Marlins  AAA
May 6, 2026
The Marlins optioned Kempner to Triple-A Jacksonville on Wednesday, Christina De Nicola of MLB.com reports.
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Recalled from Triple-A
PMiami Marlins  AAA
May 5, 2026
The Marlins recalled Kempner from Triple-A Jacksonville on Tuesday, Christina De Nicola of MLB.com reports.
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Sent to Triple-A
PMiami Marlins  AAA
March 8, 2026
The Marlins optioned Kempner to Triple-A Jacksonville on Sunday.
Analysis
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