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Justin Slaten

2026
Red Sox· RHP · throws R· 31.1 IP· 4.60 ERA· 1.37 WHIP· 137 batters faced
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Grade

His grade shows how good he has been, and at what.
Abetter than 83% of qualified pitchers at limiting bases
RelieverPower Arm

Misses bats in bunches; lives with the walks.

Slaten is comfortably above average at limiting bases

The simulator expects him to allow 0.431 bases per batter faced, better than 83% of qualified pitchers. His best skill is limiting walks (84th percentile). Short relief outings push strikeout rates up a little, so read his K% spoke with that in mind.

His grade rests on 137 batters faced, with data through 2026-09-27.

How to read this chart
Each spoke is a skill estimate adjusted for sample size, not a raw season stat, and farther out is better. A ↓ marks a stat where a lower number is better, and its spoke is flipped so farther out still means better. The middle ring marks the league median and the outer ring the league best. Percentiles compare him with 517 qualified pitchers, those with 100+ batters faced, starters and relievers together.

Plays like…

Each of these pitchers shares his archetype and sits closest to him in xEB/PA. Pick one to see him side by side with Justin Slaten.

Kevin GausmanCubsBrandon EisertPiratesCarlos RodónYankeesMichael PetersenMarlins

Pitcher type

This map shows what kind of pitcher he is, next to the league.

Pitcher type

He lands in the “Misses bats, limits hard contact” corner of the map.

League best:K% − BB% Jacob Misiorowski (26.8%)Hard-hit% allowed Blake Snell (29.0%)

How to read this chart
Two skills separate pitching styles: strikeout rate minus walk rate, where higher is better, and hard-hit rate allowed, where lower is better. The hard-hit axis is flipped, so the best corner is the top right. Each dot is a pitcher with 80+ batters faced this season, sized by batters faced. The dashed lines are the league median on each skill, and the league best on each is named above the chart. Click any dot to open that pitcher's page.
 Justin SlatenLeague medianPercentile
Bases per ball in play(lower = better).568.527—
Walk rate(lower = better)7%9%84th
Strikeout rate(higher = better)25%22%76th

A higher percentile is better, and the 99th is the top of the league.

Arsenal

These cards show what he throws and what each pitch does.

Justin Slaten mixes his cutter (42%) and four-seam fastball (25%). His best pitch has been the sinker, saving 5.1 bases per 100 thrown against league average, with a 27% whiff rate against a league median of 13%.

Pitch mix & swing-and-miss

+11 bases better than a replacement arm this season

He allowed about 61 estimated bases, against a replacement arm's 71 over the same batters faced.

Replacement level is per-batter and can't be split by pitch type, so the bars below use league average.

All pitches

He saved 0.5 bases against league average across 491 pitches, or 0.1 per 100 pitches.

Cutter
42%
93.6 mph · RHP median 90.1
18% whiffs · Lg median 22%
cost 1.6 per 1003.4 total
Four-Seam Fastball
25%
96.6 mph · RHP median 95.1
21% whiffs · Lg median 21%
saved 1.5 per 1001.9 total
Sweeper
17%
86.1 mph · RHP median 83.5
44% whiffs · Lg median 31%
cost 1.4 per 1001.3 total
Sinker
13%
97.3 mph · RHP median 94.7
27% whiffs · Lg median 13%
saved 5.1 per 1003.3 total
Curveball
not charted
3%
84.6 mph · RHP median 81.2
—
—

His curveball isn't in the charts below, because only 17 of them were tracked with velocity and movement data this season.

How to read this chart
Each row is a pitch he throws at least 3% of the time, from pitch tracking in the regular season. The bar is how often he throws it, then its average velocity and its whiff rate, the share of swings that miss. Beside the velocity and the whiff rate is the median for that pitch, among pitchers of his hand for velocity and across the league for whiffs. More whiffs are better for a pitcher, while usage and velocity describe how he pitches. The Bases vs average bars score each pitch against a league-average pitch in the same count, and a bar to the left (saved) is better.

Mix by batter side

Cutter
46% vs LHH · RHP median 20%
37% vs RHH · RHP median 19%
Four-Seam Fastball
32% vs LHH · RHP median 40%
18% vs RHH · RHP median 33%
Sweeper
10% vs LHH · RHP median 17%
24% vs RHH · RHP median 29%
How to read this chart
Each row shows how often he throws a pitch to left-handed hitters (LHH) and right-handed hitters (RHH), next to the median for pitchers of his hand (RHP median). Medians come from right-handed pitchers who throw that pitch at least 3% of the time. Between 131 and 384 of them qualify, depending on the pitch. A mix is a plan, so a higher or lower share is neither better nor worse. Overall results by batter side are under Platoon splits.

Justin Slaten's pitch movement, 2026

His Sweeper has moved 2+ inches from its early-season shape.

The verdict above compares each pitch with his own early-season outings in 2026, not with other pitchers, after taking out the league-wide drift in break.

Justin Slaten's pitch movement, 2026-1201201224in← glove sidearm side →more risemore drop
CutterFC
Rise 9.2 in
+1.5 vs Lg median
Break −2.7 in
−0.6 vs Lg median
Vs. early season steady
Four-Seam FastballFF
Rise 16.6 in
+0.9 vs Lg median
Break 1.2 in
−6.5 vs Lg median
Vs. early season steady
SweeperST
Rise 2.4 in
+1.3 vs Lg median
Break −13.7 in
+0.1 vs Lg median
Vs. early season changed
SinkerSI
Rise 15.5 in
+7.2 vs Lg median
Break 11.6 in
−3.6 vs Lg median
Vs. early season steady
Early season → nowLg medianNormal wobble around the dot
How to read this chart
Each dot is a pitch's current break in inches, averaged over his latest outings. Higher is more rise and further right is more arm-side break, and neither is better or worse. The faint trail runs from his early-season outings to the dot, and the soft halo shows how far normal noise can move it. League median is the small hollow ring, and a pitch marked * has none because too few pitchers throw it. The “changed” verdict removes a league-wide drift that the trail still shows, so a long trail can read as steady. The by-appearance chart below has the exact dates. More on the About page

By appearance

These charts follow his velocity, movement and mix from outing to outing.

These charts follow his velocity, movement and pitch mix one outing at a time, and each pitch keeps the same color in every chart. The velocity and movement charts also shade the middle of the league for scale. His curveball isn't in these charts, because only 17 of them were tracked with velocity and movement data this season.

Platoon splits

This section splits his results against lefties and righties.

Platoon splits (EB/PA allowed)

He handles righty bats better than lefty bats, by 0.041 EB/PA allowed.

50% probable range: +0.033 to +0.049

vs LHB71 PA0.437

vs LHB: shrunk estimate 0.437 EB/PA, 50% probable range 0.416 to 0.458, based on 71 plate appearances. Raw (unshrunk) rate: 0.383 EB/PA. League median vs LHB: 0.451 EB/PA.

vs RHB66 PA0.396

vs RHB: shrunk estimate 0.396 EB/PA, 50% probable range 0.376 to 0.418, based on 66 plate appearances. Raw (unshrunk) rate: 0.476 EB/PA. League median vs RHB: 0.435 EB/PA.

His raw rate vs RHB (0.476) is off this scale. Small samples can push a raw rate this far, which is why the dot, the shrunk estimate, is the number to trust.

0.3660.3910.4170.4420.468
← betterworse →
Below league medianAbove50% probable rangeHis raw rateMiddle half of the league

His split is about typical for a righty arm (median 0.042). He allows less than the league median against both sides, so even his weaker side is a strength.

How to read this chart
  • Each dot is his estimate against that side, with its 50% probable range as the bar. These are bases allowed, so lower is better.
  • The diamond is his raw rate, which small samples make noisy, so the simulator pulls the dot toward a more trustworthy value.
  • The dashed tick is the league median, and the shaded strip is the middle half of pitchers with 100 or more batters faced.
  • The two splits average back to his modeled overall EB/PA allowed, not the xEB/PA headline.
  • Tap or hover a mark for its number. LHB and RHB are left- and right-handed batters. More on the About page

Contact allowed

These cards show what hitters do when they make contact.

Batters go to the pull side off him most often, and that's also where they do the most damage.

Pull side and opposite field depend on which side each batter hits from, so this pools every hitter he faced.

Batted balls allowed

Every ball hit off Justin Slaten this season is drawn where it landed.
hit · out
EBlowhigh
vs Cody BellingerHome run
101 mph · 27° · worth 3.7 bases
06/07 vs Yankees
vs Byron BuxtonHome run
109 mph · 32° · worth 3.7 bases
05/22 vs Twins
vs Cedric MullinsHome run
104 mph · 36° · worth 3.6 bases
06/10 vs Rays
vs Austin MartinHome run
98 mph · 33° · worth 3.3 bases
05/22 vs Twins
vs Colson MontgomerySingle
101 mph · 12° · worth 1.9 bases
08/06 vs White Sox

Luck check

How to read this chart
Dot color is estimated bases (EB), what the contact was worth no matter what the defense did with it. Darker means more bases, so a dark hollow ring in the outfield is a crushed ball his defense ran down. Tap or hover a dot or a row to link the two, and use the ▶ links to watch a play on Baseball Savant.

Deserved vs. actual

Batters have been credited with about the bases their contact off Justin Slaten deserved.

Deserved by the contact he allowed51
Actually credited to batters52

Both bars count 89 balls in play, with walks and strikeouts left out.

How to read this chart
Every ball in play is worth the bases its exit velocity, launch angle and direction usually produce. If batters were credited with more than that, his results have been unlucky, and fewer means lucky. BABIP against is the batting average on balls in play he allows, next to the league median.

ERA 4.60 · WHIP 1.37 · BABIP against 0.353 (Lg median 0.286)

Best games

These are his biggest outings this season.

Best games

These are his best outings this season, ranked by bases saved against a replacement arm.

Multi-season trends · Justin Slaten

Compared with last season, his HR allowed% is up, his BB% is down, his K% is up and his Barrel% against is down.

Actual rates show what happened on the field, season by season.