Mithrandir Metrics
Pitcher projection 2026 Refreshed Sep 29 06:00 AM ET
Pitcher projection / BOS · 2026

Slaten, Justin

Late-inning arm with usable miss-bat shape

Primary
22.3% K%
Range
15.6% to 30.8%
Live Δ
yes
Team BOS Archetype Balanced reliever 2 Age 29 Status Out / inactive
At a glance

Season percentile report

The headline weighs outcome stats (xwOBA, barrels); each bar averages its full strip group below. 100 = best in MLB.

2026-09-29
67
Pitching
percentile
Pitching9 metrics
66
Arsenal5 metrics
66
Rolling projection

Preseason / current pace / Bayesian update

Rolling bands shrink current-season signal toward the preseason prior until the sample earns more weight.

2026-09-29
ERA preseason3.74
ERA current pace4.60
ERA rolling p504.07
Observed weight38%
ERA
2.60 3.30 4.07 4.85 5.55
FIP
2.71 3.08 3.48 3.88 4.25
K%
19.2% 21.6% 24.2% 26.9% 29.3%
BB%
4.8% 5.9% 7.2% 8.5% 9.6%
Current percentile strip

Actual percentile with projection tick

100th = best in MLB.

2026-09-29
Pitching · percentile strip
WHIP1.35
46
ERA4.60
34
BB%6.7%
83
K%27.5%
83 +32 vs proj
xwOBA allowed0.266
91 +41 vs proj
Barrel allowed6.2%
72
Fastball velo96.8
85
Hard-hit allowed39.2%
45
Whiff%22.9%
53
Mithrandir+

Stuff+ and arsenal context

Stuff+ appears when the current pitch-event scoring artifact includes this pitcher; Arsenal Decomposition remains descriptive support under Stuff+.

2026-09-29
Cutter Stuff+104
79
Fastball Stuff+108
88
Mithrandir Stuff+106
84
Sinker Stuff+101
39
Slider Stuff+101
39
Optimization map

Arsenal optimization map

Pitch-shape context from this pitcher’s current arsenal snapshot. Hover a pitch to inspect usage, movement, and bat-missing context.

6Pitches 2026Season 42%Top usage
ride armside gloveside +Arsenal gap +Shape contrast
Rolling form chart

xwOBA allowed snapshot line

Live snapshot series; true 50/100 PA windows require PA-level logs

12 snapshots
Mithrandir Metrics ROLLING XWOBA LINE Parameterized Mithrandir chart rendered as SVG for templates and exports. season=2026 Rolling xwOBA allowed Slaten, Justin · Live snapshot series; true 50/100 PA windows require PA-level logs LG AVG 0.313 0.266 2026-09-18: 0.2662026-09-19: 0.2662026-09-20: 0.2662026-09-21: 0.2662026-09-22: 0.2662026-09-23: 0.2662026-09-24: 0.2662026-09-25: 0.2662026-09-26: 0.2662026-09-27: 0.2662026-09-28: 0.2662026-09-29: 0.266 2026-09-18 2026-09-29 xwOBA allowed MITHRANDIR · CHARTS
Zone profile

Aggregate zone heatmap

Aggregate zone metrics from seasonal Statcast leaderboards.

Mithrandir Metrics ZONE HEATMAP Parameterized Mithrandir chart rendered as SVG for templates and exports. season=2026 Pitch Zone Profile Slaten, Justin · Aggregate zone metrics; not pitch-by-pitch locations Edge: 36%36%Zone: 52%52%Whiff: 23%23%Called strike: 16%16%First pitch strike: 49%49%Hard hit allowed: 39%39% Dashed border = aggregate mixed-batter zone proxy MITHRANDIR · CHARTS
Pitch arsenal

Usage mix, movement map, and Stuff+ composition

2026 pitch-level arsenal aggregates; current season takes over after 100 tracked pitches across at least 2 pitch types. Descriptive pitch-type Stuff+ composition. Not a promoted predictive metric.

2026
Mithrandir Metrics PITCH ARSENAL DONUT Parameterized Mithrandir chart rendered as SVG for templates and exports. Pitch Arsenal Slaten, Justin · 2026 arsenal snapshot Cutter: 42.2%4-Seam Fastball: 25.2%Sweeper: 17.2%Sinker: 11.8%Curveball: 3.4%Split-Finger: 0.2% FC42% · 93 mphprimary pitch FC 42%FF 25%ST 17%SI 12%CU 3%FS 0% MITHRANDIR · CHARTS
Mithrandir Metrics PITCH MOVEMENT Parameterized Mithrandir chart rendered as SVG for templates and exports. Pitch Arsenal Slaten, Justin · 2026 arsenal snapshot 15″30″45″60″ Cutter: 42% usage, 0″ horizontal break, 22″ drop, 93.4 mphFC93 mph4-Seam Fastball: 25% usage, 0″ horizontal break, 12″ drop, 96.5 mphFF97 mphSweeper: 17% usage, 6″ horizontal break, 35″ drop, 85.9 mphST86 mphSinker: 12% usage, 6″ horizontal break, 14″ drop, 97.3 mphSI97 mphCurveball: 3% usage, 5″ horizontal break, 52″ drop, 84.5 mphCU84 mphSplit-Finger: 0% usage, 13″ horizontal break, 32″ drop, 87.6 mphFS88 mph less drop ↑ more drop ↓ · horizontal break ↔ · dot size = usage · break incl. gravity MITHRANDIR · CHARTS
PitchUsagePitchesStuff+Status
FC 47.6% 119 104 limited sample
FB 28.4% 71 108 limited sample
SL 15.6% 39 101 limited sample
SI 5.2% 13 101 limited sample
CB 3.2% 8 101 limited sample
Method note

Renamed from the attempted Kirby Index after audit; true Kirby requires release-angle trajectory data.

Model read

Projection notes

1
templated note
Volume stays relief-shaped even when the bat-miss traits are strong.
pitcher
2
templated note
Primary mix entering the season: 4-Seam Fastball 36%, Cutter 33%, Curveball 18%.
pitcher
Live context

Current-season signal

ERA Δ+0.81
K% Δ+0.053
Sample34.0 IP

positive regression

Projection table

Point projection and range

MetricPointRangeHalf-width
Innings35.4----
Batters Faced145----
K%22.3%15.6% to 30.8%+/- 7.6%
BB%7.5%4.0% to 11.2%+/- 3.6%
Whiff%24.9%19.5% to 32.1%+/- 6.3%
HR/91.060.45 to 1.83+/- 0.69
xwOBA Against0.3120.254 to 0.355+/- 0.051
Barrel% Allowed6.9%2.9% to 10.8%+/- 4.0%
ERA3.792.29 to 6.35+/- 2.03
FIP3.752.75 to 4.87+/- 1.06
WHIP1.2300.876 to 1.545+/- 0.334
Platoon / Shape
vs LHH

174 career BF

xwOBA0.273
K%18.9%
BB%6.7%
Barrel5.2%
vs RHH

207 career BF

xwOBA0.262
K%19.1%
BB%4.3%
Barrel6.4%