Justin Slaten

ActiveIL

Boston Red Sox · RP

Age 296' 4" · 222 lbsThrows Right

#706 Current

FBaseball Overview

The 28-year-old right-hander has struggled early in 2026 after showing modest promise in his first full season last year, posting a 5.89 ERA and 1.58 WHIP through 18 innings while striking out 23 batters. His 2025 campaign demonstrated he could be effective in relief with a 4.24 ERA, 1.09 WHIP, and three saves across 34 innings, suggesting upside if he can return to that form. Fantasy managers should view Slaten as a high-risk, mid-tier option whose value hinges on whether Boston utilizes him in a high-leverage role; his strikeout rate shows some fantasy appeal, but early-season control issues and inflated ERA create concern for categories like WHIP and wins. Monitor his next month of performance closely, as a correction toward 2025 numbers could make him a worthwhile bench stash, while continued struggles would warrant looking elsewhere.

MLB Pitching

Year	Team	G	W	L	SV	ERA	WHIP	K	IP	BB
2024	Boston Red Sox	44	6	2	2	2.93	1.01	58	55.1	9
2025	Boston Red Sox	36	2	4	3	4.24	1.09	25	34.0	10
2026	Boston Red Sox	36	2	4	0	4.60	1.37	39	31.1	8
Career	Totals	116	10	10	5	3.73	1.13	122	120.2	27

Source: MLB Stats API · Multi-team seasons show combined totals — click to expand

Minor League Pitching

Year	Team	G	GS	W	L	SV	ERA	WHIP	K	IP	BB
2019	2 teams▼	11	10	0	2	0	6.06	1.71	22	16.1	7
2021	Hickory Crawdads	20	19	4	8	0	6.01	1.51	110	82.1	31
2022	2 teams▼	26	5	1	6	0	6.79	1.88	66	51.2	48
2023	2 teams▼	40	1	5	3	2	2.87	1.07	86	59.2	20
2024	Portland Sea Dogs	1	0	0	0	0	27.00	6.00	1	0.1	1
2025	Worcester Red Sox	3	0	1	0	0	0.00	0.67	5	3.0	1
2026	2 teams▼	2	2	0	0	0	0.00	1.50	4	2	1
Career	Totals	103	37	11	19	2	5.22	1.49	294	215.1	109

Source: MLB Stats API · Multi-team seasons show combined totals — click to expand

Last Week / Last Month

Current season · MLB only

7 games

G	GS	IP	W-L	SV	ERA	WHIP	K	BB
7	0	5.2	1-0	0	3.18	1.24	5	2

30 games

G	GS	IP	W-L	SV	ERA	WHIP	K	BB
30	0	26.0	2-3	0	5.54	1.46	33	6

Game Log2026 MLB

Loading game log…

Advanced Stats2026 season · via Baseball Savant

Click for year to year changes

FB Velo96.8 mph

Avg Spin2513 rpm

Whiff %25.2%

K %28.5%

BB %5.8%

Hard Hit %36.7%

Barrel %4.4%

xERA2.94

xBA Against0.223

xSLG Against0.331

BA Against0.276

SLG Against0.417

What These Stats Mean

FB Velo — Average fastball velocity. Harder throwers generate more swings and misses, setting up every other pitch in their arsenal. Velocity is the foundation of strikeout upside.

Avg Spin — Average spin rate across all pitches. Higher spin creates more movement and makes pitches harder to square up — elite spinners run better strikeout and batting average against numbers.

Whiff % — Swings-and-misses per swing. The most direct measure of a pitcher's ability to miss bats and the best leading indicator of strikeout rate.

K % — Strikeout rate per batter faced. The core fantasy pitching stat — high K% means reliable strikeout totals that hold up even in shorter starts.

BB % — Walk rate per batter faced. The primary control metric. High BB% tanks ERA and WHIP and keeps baserunners on constantly. Elite starters typically run below 7%.

Hard Hit % — Percentage of batted balls hit 95 mph or harder against. Low hard-hit% means weak contact, protecting both ERA and the defense behind the pitcher.

Barrel % — Percentage of batted balls barreled against. The most direct home run predictor — low barrel% pitchers rarely give up long balls.

xERA — Expected ERA based on contact quality allowed, removing the effect of sequencing, luck, and defense. Better predictor of future ERA than ERA itself.

xBA Against — Expected batting average opponents should hit based on contact quality. A gap between xBA and actual BA indicates unsustainable luck in either direction.

xSLG Against — Expected slugging allowed based on contact quality. High xSLG against predicts future extra-base damage; low xSLG means the pitcher is genuinely suppressing power.

BA Against — Actual batting average opponents are hitting — a key WHIP component. Check xBA to see if the number is sustainable.

SLG Against — Actual slugging allowed. Captures hits, doubles, triples, and home runs — lower means the pitcher is limiting the power damage he gives up.

GB% — Ground ball rate. High GB% pitchers generate double plays, limit home runs, and keep the ball in the park — great for protecting ERA and WHIP ratios.

FB% — Fly ball rate. High FB% pitchers give up more air contact — dangerous when combined with high exit velocity, less so when contact is soft.

Loading player data...

Year

Team

ERA

WHIP

2024

Boston Red Sox

2.93

1.01

55.1

2025

Boston Red Sox

4.24

1.09

34.0

2026

Boston Red Sox

4.60

1.37

31.1

Career

Totals

116

3.73

1.13

122

120.2

Year

Team

ERA

WHIP

2019

2 teams▼

6.06

1.71

16.1

2021

Hickory Crawdads

6.01

1.51

110

82.1

2022

2 teams▼

6.79

1.88

51.2

2023

2 teams▼

2.87

1.07

59.2

2024

Portland Sea Dogs

27.00

6.00

0.1

2025

Worcester Red Sox

0.00

0.67

3.0

2026

2 teams▼

0.00

1.50

Career

Totals

103

5.22

1.49

294

215.1

109

W-L

ERA

WHIP

5.2

1-0

3.18

1.24

W-L

ERA

WHIP

26.0

2-3

5.54

1.46