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Justin Slaten

#63 - Relief Pitcher

Boston Red Sox

Bats / Throws Right / Right
Date of Birth 9/15/1997 (27)
Height, Weight 6'4", 222 lb
Hometown Longview, TX

2025 Season Stats

MLB Rank MLB Average
Sv IP ERA WHIP K% BB%
2 8.0 4.50 0.63 25.0% 3.1%
24th 1
Sv
152nd 7
IP
205th 4.83
ERA
30th 1.46
WHIP
140th 22.4%
K%
55th 10.0%
BB%
FB MPH SwStr% CSW% Str-ICR MTK% PLV PLA
97.0 18.6% 31.9% 56.6% 6.2% 5.26 2.11
39th 93.9
FB MPH
51st 12.4%
SwStr%
124th 28.4%
CSW%
116th 49.5%
Str-ICR
200th 5.3%
MTK%
51st 4.97
PLV
23rd -
PLA
Saves List
Rank
40th
Holds List
Rank
15th
Saves+Holds List
Rank
34th

Articles

4/20/2025Waiver Relief: 4/20/2025Alex Kamberis

4/20/20252025 Fantasy Baseball Week 4 FAAB InsightsBrett Ford

4/18/2025RP Ranks 4/18: The Top 100 Relievers for Save+Hold LeaguesRick Graham

4/11/2025RP Ranks 4/11: The Top 100 Relievers for Save+Hold LeaguesRick Graham

4/4/2025RP Ranks 4/4: The Top 100 Relievers for Save+Hold LeaguesRick Graham

See More Articles
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Justin Slaten Overview

Hide 2025 MLB Percentile | Hide 2025 MLB Average
Year Team G GS IP W-L Sv Hld ERA WHIP xERA FIP xFIP PLA K% BB% H/9 HR/9 BABIP HR/FB% LOB% ICR GB% SwStr% CSW% IPR PLV
2024 BOS 44 0 55.1 6-2 2 13 2.93 1.01 2.77 2.60 2.96 2.67 25.9% 4.0% 7.6 0.65 .285 13.3% 70.6% 38.1% 50.6% 15.5% 29.3% 0.55 5.11
2025 BOS 9 0 8.0 0-0 2 0 4.50 0.63 1.21 1.66 3.38 2.11 25.0% 3.1% 4.5 0.00 .174 0.0% 20.0% 30.4% 26.1% 18.6% 31.9% 0.61 5.26
RP MLB Percentile 59 0 46 0-25 90 0 35 90 94 88 68 93 57 83 77 54 78 59 1 62 14 83 62 56 83
RP MLB AVG 7 0 7.0 0-0 1 1 4.83 1.46 4.77 4.74 4.60 3.46 22.4% 10.0% 8.8 1.16 .289 17.8% 73.8% 39.3% 44.2% 12.4% 28.4% 0.49 4.97
Career 53 0 63.1 6-2 4 13 3.13 0.96 - - - 2.60 25.8% 3.9% 7.2 0.57 .270 10.5% 66.2% 37.1% 47.5% 15.9% 29.7% 0.56 5.12

Justin Slaten Repertoire

2024 2025 All
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Justin Slaten Game Log

Justin Slaten Standard

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Year Team G GS IP W-L QS Sv Hld P Strikes Balls TBF H 1B 2B 3B HR K BB HB WP
2024 BOS 44 0 55.1 6-2 0 2 13 811 546 265 224 47 36 6 1 4 58 9 2 4
2025 BOS 9 0 8.0 0-0 0 2 0 113 78 35 32 4 4 0 0 0 8 1 0 0
RP MLB Percentile 59 0 46 0-25 0 90 0 32 35 69 36 64 38 69 11 53 46 72 31 25
RP MLB AVG 7 0 7.0 0-0 0 1 1 121 77 44 31 6 4 1 0 1 7 3 0 0
Career 53 0 63.1 6-2 0 4 13 924 624 300 256 51 40 6 1 4 66 10 2 4

Justin Slaten Advanced

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Year Team K% BB% AVG SLG OPS wOBA BABIP BACON xAVG xwOBA xBABIP xwoBACON EV FB EV LA xERA
2024 BOS 25.9% 4.0% .223 .318 .577 .253 .285 .303 .214 .259 .264 .326 87.6 89.4 8.9 2.77
2025 BOS 25.0% 3.1% .129 .129 .285 .133 .174 .174 .137 .158 .185 .189 88.5 90.2 19.5 1.21
RP MLB Percentile 57 83 79 87 93 94 78 83 85 94 83 89 53 54 30 94
RP MLB AVG 22.4% 10.0% .241 .391 .717 .318 .289 .317 .239 .322 .282 .364 88.4 89.8 12.9 4.77
Career 25.8% 3.9% .211 .293 .539 .241 .270 .287 .204 .249 .253 .312 87.7 89.6 10.3 -

Justin Slaten Pitch › Mix

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Year Team FF% (MPH) SI% (MPH) FC% (MPH) SL% (MPH) ST% (MPH) CB% (MPH) CH% (MPH) FS% (MPH) KN% (MPH) Fastball% Secondary%
2024 BOS 29.2% (96.4) - 37.7% (91.5) - 24.5% (84.0) 8.4% (84.3) - - - 29.2% 70.7%
2025 BOS 35.6% (96.8) - 33.7% (92.5) - 11.9% (84.8) 18.8% (85.1) - - - 35.6% 64.4%
RP MLB Percentile 41 (84) - 73 (91) - 18 (84) 62 (90) - - - 20.9% 78.8%
RP MLB AVG 38.4% (93.9) 28.5% (93.5) 26.5% (89.4) 29.2% (85.6) 25.2% (81.9) 19.5% (80.3) 20.0% (85.9) 21.8% (86.9) - (-) 47.6% 52.3%
Career 29.9% (96.4) - 37.3% (91.6) - 23.1% (-) 9.5% (84.5) - - - 29.9% 70.0%

Justin Slaten Pitch › Results

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Year Team FF CSW% SI CSW% FC CSW% SL CSW% ST CSW% CB CSW% CH CSW% FS CSW% KN CSW% Fastball CSW% Secondary CSW%
2024 BOS 29.1% (33) - 29.4% (40) - 28.6% (42) 32.4% (11) - - - 29.1% 29.5%
2025 BOS 25.0% (5) - 35.3% (5) - 33.3% (3) 26.3% (4) - - - 25.0% 32.3%
RP MLB Percentile 38 (41) - 77 (22) - 51 (51) 41 (22) - - - 34.7% 62.9%
RP MLB AVG 26.8% (5) 28.3% (3) 27.6% (4) 30.8% (6) 30.9% (5) 28.7% (3) 23.1% (4) 26.1% (6) - (-) 27.4% 29.0%
Career 28.6% (38) - 30.0% (45) - 28.9% (45) 31.0% (15) - - - 28.6% 29.8%

Justin Slaten Batted Ball › Contact

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Year Team GB% LD% FB% PU% SS% Pull% Cent% Oppo% Foul Str% PC% Fl&B% Solid% Brl% ICR
2024 BOS 50.6% 20.8% 19.5% 9.1% 31.2% 44.2% 35.7% 20.1% 18.9% 61.6% 27.3% 7.1% 3.9% 38.1%
2025 BOS 26.1% 26.1% 34.8% 13.0% 43.5% 30.4% 39.1% 30.4% 16.8% 69.5% 21.7% 4.3% 4.3% 30.4%
RP MLB Percentile 14 23 66 74 23 23 66 64 44 63 44 51 61 62
RP MLB AVG 44.2% 21.6% 24.1% 10.1% 34.7% 41.3% 33.5% 25.2% 17.5% 61.6% 23.8% 6.3% 8.2% 39.3%
Career 47.5% 21.5% 21.5% 9.6% 32.8% 42.4% 36.2% 21.5% 18.6% 62.8% 26.6% 6.8% 4.0% 37.1%

Justin Slaten Batted Ball › Outcomes

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Year Team AVG wOBA BABIP BACON xAVG xwOBA xBABIP xwoBACON EV FB EV LA HR/FB ICR IPA%
2024 BOS .223 .253 .285 .303 .214 .259 .264 .326 87.6 89.4 8.9 13.3% 38.1% 26.3%
2025 BOS .129 .133 .174 .174 .137 .158 .185 .189 88.5 90.2 19.5 0.0% 30.4% 21.9%
RP MLB Percentile 79 94 78 83 85 94 83 89 53 54 30 59 62 56
RP MLB AVG .241 .318 .289 .317 .239 .322 .282 .364 88.4 89.8 12.9 17.8% 39.3% 26.5%
Career .211 .241 .270 .287 .204 .249 .253 .312 87.7 89.6 10.3 10.5% 37.1% 25.8%

Justin Slaten Approach › Plate Discipline

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Year Team Zone% Str% Swing% O-Sw% Whiff% Foul Str% Con% Z-Con% O-Con% CS% SwStr% CSW% BIP% PLUS% IPR Str-ICR
2024 BOS 46.6% 67.3% 53.5% 37.0% 29.0% 18.9% 71.0% 85.4% 46.3% 13.8% 15.5% 29.3% 19.1% 61.5% 0.55 52.8%
2025 BOS 47.8% 69.0% 55.8% 39.0% 33.3% 16.8% 66.7% 67.5% 65.2% 13.3% 18.6% 31.9% 20.4% 65.5% 0.61 56.6%
RP MLB Percentile 41 76 88 86 72 44 72 88 30 22 83 62 83 83 56 64
RP MLB AVG 45.7% 63.1% 47.1% 30.1% 26.0% 17.5% 74.0% 82.9% 56.5% 16.0% 12.4% 28.4% 17.2% 57.7% 0.49 49.5%
Career 46.8% 67.5% 53.8% 37.2% 29.6% 18.6% 70.4% 83.1% 48.6% 13.7% 15.9% 29.7% 19.3% 62.0% 0.56 53.2%

Justin Slaten Approach › Locations

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Year Team Zone% aLoc% x-mLoc% gLoc% hiLoc% y-mLoc% loLoc% iLoc% oLoc% mmLoc%
2024 BOS 46.6% 22.5% 33.1% 44.4% 32.5% 19.1% 48.4% 29.8% 37.2% 6.2%
2025 BOS 47.8% 22.1% 30.1% 47.8% 24.8% 15.9% 59.3% 24.8% 45.1% 4.4%
RP MLB Percentile 41 14 13 70 27 95 95 13 59 14
RP MLB AVG 45.7% 34.7% 25.7% 39.6% 31.3% 24.7% 44.1% 30.1% 44.2% 6.6%
Career 46.8% 22.4% 32.7% 44.9% 31.5% 18.7% 49.7% 29.1% 38.1% 6.0%

Justin Slaten Approach › Counts

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Year Team Early% Behind% 2-Str% Early BIP% F-Str% TF-Str% ECS% 2-Str O-Sw% PAR%
2024 BOS 60.9% 10.5% 28.7% 18.0% 63.4% 48.2% 17.2% 26.6% 24.9%
2025 BOS 62.8% 8.0% 29.2% 15.5% 62.5% 53.1% 16.9% 27.3% 24.2%
RP MLB Percentile 85 79 41 75 45 41 19 66 72
RP MLB AVG 58.5% 12.5% 29.6% 14.1% 58.9% 48.5% 20.6% 25.0% 19.3%
Career 61.1% 10.2% 28.8% 17.7% 63.3% 48.8% 17.2% 26.7% 24.8%

Justin Slaten PLV

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Year Team P PLV QP% AP% BP% Q-BP% MTK% HP HL PLA
2024 BOS 811 5.11 46.8% 19.1% 34.0% 12.8% 4.9% -3.3 +10 2.67
2025 BOS 113 5.26 51.3% 20.4% 28.3% 23.0% 6.2% -4.8 -2 2.11
RP MLB Percentile 32 83 77 76 89 89 37 94 75 93
RP MLB AVG 121 4.97 45.8% 18.2% 36.0% 9.8% 5.3% - +1 3.46
Career 924 5.12 47.4% 19.3% 33.3% 14.0% 5.0% -8.0 +8 2.60
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