Jackson Kowar

Jackson Kowar

28-Year-Old PitcherRP
Seattle Mariners
2025 Fantasy Outlook
There was no outlook written for Jackson Kowar in 2025. Check out the latest news below for more on his current fantasy value.
$Signed a one-year contract with the Mariners in March of 2025.
Reinstated from IL
PSeattle Mariners
May 28, 2025
The Mariners reinstated Kowar (elbow) from the 60-day injured list Wednesday.
ANALYSIS
Kowar will return to the majors after missing the entire 2024 season following Tommy John surgery last March. The 28-year-old right hander posted a 2.57 ERA and 1.29 WHIP across seven innings during his rehab assignment and did not yield a run in each of his last three outings. Kowar will be available to make his 2025 debut out of the Mariners' bullpen against the Nationals on Wednesday. Logan Evans was optioned to Triple-A Tacoma in a corresponding move.
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Pitching Stats
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2025
2024
2023
2022
2021
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2024 MLB Game Log
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2023 MLB Game Log
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2022 MLB Game Log
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Pitching Appearances Breakdown
Average Pitch Count
20
Last 10 Games
20
Last 5 Games
20
How many pitches does Jackson Kowar 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 Jackson Kowar 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 2023
 
 
-1%
BAA vs RHP
2025
 
 
-100%
BAA vs RHP
2024
No Stats
2023
 
 
-6%
BAA vs RHP
BAA Batters K BB H 2B 3B HR
Since 2023vs Left .281 65 10 7 16 2 0 1
Since 2023vs Right .278 86 21 13 20 6 0 3
2025vs Left .182 12 1 0 2 1 0 0
2025vs Right .000 2 1 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
2023vs Left .304 53 9 7 14 1 0 1
2023vs Right .286 84 20 13 20 6 0 3
More Splits View More Split Stats
Home/Away Pitching Splits
Since 2023
 
 
-83%
ERA at Home
2025
No Stats
2024
No Stats
2023
 
 
-78%
ERA at Home
ERA WHIP IP W L SV K/9 BB/9 HR/9
Since 2023Home 1.65 0.92 16.1 2 0 0 9.4 2.2 0.0
Since 2023Away 9.77 2.62 15.2 0 0 0 8.0 9.2 2.3
2025Home 0.00 0.50 4.0 0 0 0 4.5 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
2023Home 2.19 1.05 12.1 2 0 0 10.9 2.9 0.0
2023Away 9.77 2.62 15.2 0 0 0 8.0 9.2 2.3
More Splits View More Split Stats
Stat Review
How does Jackson Kowar 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
4.5
 
BB/9
0.0
 
HR/9
0.0
 
Fastball
97.7 mph
 
ERA
0.00
 
WHIP
0.50
 
BABIP
.177
 
GB/FB
0.43
 
Left On Base
100.0%
 
Exit Velocity
81.6 mph
 
Barrels/BBE
0.0%
 
Spin Rate
2289 rpm
 
Balls Hit 95+ MPH
16.7%
 
Swinging Strike
9.8%
 
Prospect Rankings History
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 Jackson Kowar See More
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Past Fantasy Outlooks
2023
2021
2020
An ugly 2022 campaign took a lot of shine out of Kowar's prospect stock. He worked as a starter with Triple-A Omaha, but a 6.16 ERA and 1.66 WHIP over 83.1 innings at that level easily made his worst minor-league season. Despite the struggles, he also made seven relief appearances in the majors, and the results were even worse -- a 9.77 ERA and 2.43 WHIP across 15.2 innings. With 46 big-league innings to his name in the majors, it's too early to write off the right-hander, but it's fair to question if his stuff is good enough. His 96 mph fastball didn't miss many bats, though he uses a very effective changeup almost as often, with that pitch racking up a 35 whiff rate in the majors. He'll likely be in the minors or in the rotation in 2023, as the Royals will probably want to give him one more chance to prove himself as a starter, but he's got work to do.
Kowar hasn't been hyped up the way org. mates Asa Lacy and Daniel Lynch have, but with a mid-90s fastball and one of the best changeups in the minors, he belongs in that same conversation. His Florida teammate Brady Singer beat him to the majors, but Singer was always seen as a quick-to-the-majors guy, while Kowar was more of a high-upside pitcher who would require more development. A lean 6-foot-5, Kowar worked on repeating his delivery and honing his command at the alternate site. Perhaps most importantly, he made impressive strides with his third-pitch curveball. Royals officials think he only needs an average curve to pitch near the top of the rotation, thanks to the quality of his fastball and changeup. He should head to Triple-A and will join the big-league rotation whenever the team thinks his command and consistency warrant the promotion.
Part of the Royals' potentially historic 2018 pitcher-heavy draft class, Kowar has been incredibly consistent on his march to the majors. He made 13 starts apiece at High-A and Double-A, logging almost identical ERA, FIP, WHIP and GB% at both stops. Kowar increased his dominance and efficiency (14.1 K-BB% at High-A, 18.4 K-BB% at Double-A) against tougher competition, and should begin his age-23 season at Triple-A. His 70-grade changeup may be the best pitch of any of the pitchers Kansas City selected in that draft. Hitters can't just sit on his low-to-mid-90s fastball, because if they do, his changeup will eat them alive. His fringe-average breaking ball is a distant third pitch, and its development will be critical to Kowar becoming a good No. 3 starter, rather than an acceptable No. 4 starter. His above-average control and advanced pitchability should allow him to make the most of his arsenal.
More Fantasy News
Closing in on return
PSeattle Mariners
Elbow
May 27, 2025
Kowar (elbow) could be nearing his activation from the 60-day injured list, MLB.com reports.
ANALYSIS
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Moves to 60-day IL
PSeattle Mariners
Elbow
March 2, 2025
Kowar (elbow) was placed on the 60-day injured list Sunday, Daniel Kramer of MLB.com reports.
ANALYSIS
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Completes bullpen session
PSeattle Mariners
Elbow
February 17, 2025
Kowar (elbow) threw a bullpen session Monday, Ryan Divish of The Seattle Times reports.
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Requires Tommy John surgery
PSeattle Mariners
Elbow
March 10, 2024
The Mariners placed Kowar on the 60-day injured list Sunday after he was diagnosed with a torn UCL in his right elbow. He'll undergo Tommy John surgery next Friday in Dallas, Daniel Kramer of MLB.com reports.
ANALYSIS
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Getting sore arm checked out
PSeattle Mariners
Arm
March 7, 2024
Kowar will meet with a doctor Friday to have his sore right arm examined, Ryan Divish of The Seattle Times reports.
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Latest Fantasy Rumors
Will switch to bullpen
PKansas City Royals
May 18, 2023
Kowar is expected to come out of the bullpen going forward, Jaylon Thompson of the Kansas City Star.
ANALYSIS
Kowar has been tabbed as a top pitching prospect since being selected with the 33rd overall pick in the 2018 MLB Draft, but he hasn't panned out as a starter to this point, and now the Royals have decided to take a look at him as a relief option. He's made 12 of his 13 Triple-A appearances out of the bullpen, and the results haven't been encouraging. The 26-year-old has posted a 7.00 ERA with 22 strikeouts and 15 walks across 18 relief innings. However, the organization still rates him highly, and manager Matt Quatraro told Thompson earlier this week that the Royals see Kowar as "someone we can count on going forward."
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