William Kempner

William Kempner

24-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.
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.
Analysis
Kempner was summoned Tuesday from the minors and made his major-league debut in Miami's 9-7 loss to Baltimore with a perfect inning out of the bullpen. He'll make room on the roster for a fresh bullpen arm in Dax Fulton, who was called up from Jacksonville in a corresponding move.
Read More News
Pitching Stats
Loading Pitching Stats...
2026 MLB Game Log
2026
2026 MLB Game Log
Calculate Stats Over Time
Just click on any two dates.
Scoring
FanDuel
DraftKings
Yahoo DFS
Sorare
Loading Pitching Game Log...
Minor League Game Log
Calculate Stats Over Time
Just click on any two dates.
Loading Minor League Pitching Game Log...
Pitching Appearances Breakdown
Average Pitch Count
8
Last 10 Games
8
Last 5 Games
8
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
No Stats
2026
No Stats
2025
No Stats
2024
No Stats
BAA Batters K BB H 2B 3B HR
Since 2024vs Left .000 1 1 0 0 0 0 0
Since 2024vs Right .000 2 0 0 0 0 0 0
2026vs Left .000 1 1 0 0 0 0 0
2026vs Right .000 2 0 0 0 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 0.00 1.0 0 0 0 9.0 0.0 0.0
Since 2024Away 0 0 0 0 0 0 0 0 0
2026Home 0.00 0.00 1.0 0 0 0 9.0 0.0 0.0
2026Away 0 0 0 0 0 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
 
 
-34%
BAA vs LHP
2026
 
 
-17%
BAA vs LHP
2025
 
 
-48%
BAA vs LHP
2024
No Stats
BAA Batters K BB H 2B 3B HR
Since 2024vs Left .145 72 31 12 8 1 0 3
Since 2024vs Right .220 75 28 14 13 1 0 2
2026vs Left .208 31 16 4 5 1 0 2
2026vs Right .250 40 18 7 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
0.00
 
K/9
9.0
 
BB/9
0.0
 
HR/9
0.0
 
Fastball
97.4 mph
 
ERA
0.00
 
WHIP
0.00
 
BABIP
.000
 
GB/FB
1.00
 
Left On Base
0.0%
 
Exit Velocity
91.5 mph
 
Barrels/BBE
0.0%
 
Spin Rate
2690 rpm
 
Balls Hit 95+ MPH
0.0%
 
Swinging Strike
12.5%
 
Advanced Pitching Stats
Loading Advanced Pitching Stats...
Defensive Stats
Loading MLB Defensive Stats...
Stats Vs Today's Lineup
Want more matchup stats?
Loading Matchup Stats...
Our full team depth charts are reserved for RotoWire subscribers.
Subscribe Now
Recent RotoWire Articles Featuring William Kempner See More
Recent RotoWire Articles Featuring William Kempner See More
More Fantasy News
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.
Analysis
Subscribe now to instantly reveal our take on this news.
Sent to Triple-A
PMiami Marlins  AAA
March 8, 2026
The Marlins optioned Kempner to Triple-A Jacksonville on Sunday.
Analysis
Subscribe now to instantly reveal our take on this news.
Joins 40-man roster
PMiami Marlins  AAA
November 18, 2025
The Marlins selected Kempner's contract from Triple-A Jacksonville on Tuesday.
Analysis
Subscribe now to instantly reveal our take on this news.
Traded to Miami
PMiami Marlins  AAA
January 15, 2025
The Marlins acquired Kempner from the Giants on Wednesday in exchange for international bonus pool space, Justice delos Santos of The San Jose Mercury News reports.
Analysis
Subscribe now to instantly reveal our take on this news.
Heads to Giants in Round 3
PSan Francisco Giants  AAA
July 18, 2022
The Giants have selected Kempner with the 106th overall pick in the 2022 first-year player draft.
Analysis
Subscribe now to instantly reveal our take on this news.