Justin Slaten

Justin Slaten

27-Year-Old PitcherRP
Boston Red Sox
2025 Fantasy Outlook
Slaten, a 2019 draft pick by the Rangers, was selected by the Mets during the Rule 5 Draft last offseason. The 26-year-old was subsequently traded to Boston and impressed his new club during Grapefruit League play, flashing upper-90's velocity. Unsurprisingly, he made the Red Sox Opening Day roster and remained with the team all year. Slaten was an immediate fixture in Boston's high-leverage hierarchy, mixing four pitches effectively to a 2.93 ERA, 1.01 WHIP and 58:9 K:BB across 55.1 frames. The rookie right-hander recorded 10 or more strikeouts on all four of his offerings, including 18 apiece on his four-seamer and sweeper. Elbow inflammation cost Slaten a month-and-a-half last summer, but it's exciting to think about what he could offer in a full season. Red Sox manager Alex Cora said in the past that he envisions Slaten as a potential long-term closer option and he certainly has the talent to emerge out of a save share with Liam Hendriks and Aroldis Chapman in 2025. Read Past Outlooks
RANKS
Rest of Season From Preseason
#393
ADP
$Signed a one-year contract with the Red Sox in March of 2025.
Slams door for second save
PBoston Red Sox
April 16, 2025
Slaten earned the save after throwing a clean ninth inning in Wednesday's win over the Rays. He struck out two.
ANALYSIS
Slaten faced little resistance, retiring the side on just 11 pitches (eight strikes) for his second save of the season. Aroldis Chapman remains the favorite for save opportunities out of the Boston bullpen, although the left-hander can cede the occasional chance based on certain matchups. The right-handed Slaten, who now holds a 5.14 ERA, 0.71 WHIP and 5:1 K:BB through seven innings, was called upon to face three right-handed batters Wednesday.
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Pitching Stats
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2025
2024
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2024 MLB Game Log
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Pitching Appearances Breakdown
Average Pitch Count
11
Last 10 Games
11
Last 5 Games
11
How many pitches does Justin Slaten 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 Justin Slaten 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
 
 
-26%
BAA vs LHP
2025
 
 
-40%
BAA vs LHP
2024
 
 
-25%
BAA vs LHP
2023
No Stats
BAA Batters K BB H 2B 3B HR
Since 2023vs Left .179 116 33 9 19 4 0 2
Since 2023vs Right .241 137 32 1 32 2 1 2
2025vs Left .100 11 2 1 1 0 0 0
2025vs Right .167 18 5 0 3 0 0 0
2024vs Left .188 105 31 8 18 4 0 2
2024vs Right .252 119 27 1 29 2 1 2
2023vs Left 0 0 0 0 0 0 0 0
2023vs Right 0 0 0 0 0 0 0 0
More Splits View More Split Stats
Home/Away Pitching Splits
Since 2023
 
 
-64%
ERA at Home
2025
 
 
-100%
ERA at Home
2024
 
 
-54%
ERA at Home
2023
No Stats
ERA WHIP IP W L SV K/9 BB/9 HR/9
Since 2023Home 1.59 0.78 28.1 3 0 1 8.6 1.3 0.6
Since 2023Away 4.37 1.11 35.0 3 2 3 9.8 1.5 0.5
2025Home 0.00 0.00 3.0 0 0 0 9.0 0.0 0.0
2025Away 7.20 1.00 5.0 0 0 2 7.2 1.8 0.0
2024Home 1.78 0.87 25.1 3 0 1 8.5 1.4 0.7
2024Away 3.90 1.13 30.0 3 2 1 10.2 1.5 0.6
2023Home 0 0 0 0 0 0 0 0 0
2023Away 0 0 0 0 0 0 0 0 0
More Splits View More Split Stats
Stat Review
How does Justin Slaten 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
7.00
 
K/9
7.9
 
BB/9
1.1
 
HR/9
0.0
 
Fastball
96.9 mph
 
ERA
4.50
 
WHIP
0.63
 
BABIP
.204
 
GB/FB
0.67
 
Left On Base
20.0%
 
Exit Velocity
84.3 mph
 
Barrels/BBE
3.3%
 
Spin Rate
2485 rpm
 
Balls Hit 95+ MPH
13.3%
 
Swinging Strike
14.9%
 
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 Justin Slaten See More
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10 days ago
Brad Johnson dives deep into some bullpens in flux, including in Detroit where injured closer Alex Lange needs to work on finding the strike zone once he's back on the mound.
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21 days ago
The American League free-agent pool features a lot of targets after the first full weekend of the season including top Red Sox prospect Kristian Campbell, who looks like he's in Boston to stay.
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28 days ago
The American League waiver wire is packed with options as Opening Day approaches, and the return of Nolan Jones to the Cleveland Guardians should settle their murky right field situation.
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29 days ago
Mason Miller makes a big jump in Ryan Rufe's updated closer rankings.
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31 days ago
Several job battles have been settled around the American League, including the Royals' fifth starter job, which appears to have been won by Kris Bubic.
More Fantasy News
Notches save in opener
PBoston Red Sox
March 28, 2025
Slaten struck out one and didn't allow a baserunner in a scoreless ninth inning to earn the save Thursday against the Rangers.
ANALYSIS
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Works scoreless inning
PBoston Red Sox
March 8, 2025
Slaten allowed a hit and struck out two over a scoreless inning in Friday's spring game against Miami.
ANALYSIS
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Notches second save
PBoston Red Sox
September 29, 2024
Slaten allowed one hit and zero walks in a scoreless ninth inning to pick up his second save of the season in Sunday's season finale against Tampa Bay.
ANALYSIS
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Candidate for saves
PBoston Red Sox
September 23, 2024
Red Sox manager Alex Cora said Sunday that he will "mix and match" at closer with Slaten and Chris Martin following the season-ending injury to Kenley Jansen (shoulder), Gabrielle Starr of the Boston Herald reports.
ANALYSIS
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Returns to mound Monday
PBoston Red Sox
August 27, 2024
Slaten struck out one over a scoreless inning in the second game of Monday's doubleheader against Toronto.
ANALYSIS
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