Mithrandir Metrics
Pitcher projection 2026 Refreshed Sep 26 06:00 AM ET
Pitcher projection / BOS · 2026

Chapman, Aroldis

High-leverage relief profile with bat-miss

Primary
34.2% K%
Range
27.4% to 43.2%
Live Δ
yes
Team BOS Archetype Balanced reliever Age 38 Status Healthy / active roster
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.

2026-09-26
78
Pitching
percentile
Pitching9 metrics
75
Arsenal4 metrics
80
Rolling projection

Preseason / current pace / Bayesian update

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

2026-09-26
ERA preseason3.48
ERA current pace1.95
ERA rolling p502.74
Observed weight49%
ERA
1.22 1.94 2.74 3.54 4.26
FIP
1.90 2.35 2.85 3.35 3.81
K%
29.4% 31.6% 33.9% 36.3% 38.4%
BB%
8.0% 9.2% 10.6% 12.0% 13.3%
Current percentile strip

Actual percentile with projection tick

100th = best in MLB.

2026-09-26
Pitching · percentile strip
WHIP1.20
73
ERA1.95
96
BB%10.9%
27
K%33.2%
97
xwOBA allowed0.252
96
Barrel allowed7.1%
56 +19 vs proj
Fastball velo97.4
91
Hard-hit allowed37.8%
54
Whiff%27.2%
82
Mithrandir+

Stuff+ and arsenal context

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

2026-09-26
Fastball Stuff+106
77
Mithrandir Stuff+108
95
Sinker Stuff+110
95
Slider Stuff+102
52
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.

4Pitches 2026Season 37%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 Chapman, Aroldis · Live snapshot series; true 50/100 PA windows require PA-level logs LG AVG 0.313 0.252 2026-09-12: 0.2552026-09-13: 0.2562026-09-14: 0.2562026-09-18: 0.2562026-09-19: 0.2562026-09-20: 0.2562026-09-21: 0.2562026-09-22: 0.2562026-09-23: 0.2562026-09-24: 0.2532026-09-25: 0.2532026-09-26: 0.252 2026-09-12 2026-09-26 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 Chapman, Aroldis · Aggregate zone metrics; not pitch-by-pitch locations Edge: 38%38%Zone: 49%49%Whiff: 27%27%Called strike: 15%15%First pitch strike: 52%52%Hard hit allowed: 38%38% 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 Chapman, Aroldis · 2026 arsenal snapshot 4-Seam Fastball: 37.3%Sinker: 31.6%Slider: 18.6%Split-Finger: 12.5% FF37% · 97 mphprimary pitch FF 37%SI 32%SL 19%FS 12% MITHRANDIR · CHARTS
Mithrandir Metrics PITCH MOVEMENT Parameterized Mithrandir chart rendered as SVG for templates and exports. Pitch Arsenal Chapman, Aroldis · 2026 arsenal snapshot 9″18″27″36″ 4-Seam Fastball: 37% usage, 1″ horizontal break, 11″ drop, 96.9 mphFF97 mphSinker: 32% usage, 5″ horizontal break, 12″ drop, 98.0 mphSI98 mphSlider: 19% usage, 1″ horizontal break, 32″ drop, 85.9 mphSL86 mphSplit-Finger: 12% usage, 4″ horizontal break, 31″ drop, 90.0 mphFS90 mph less drop ↑ more drop ↓ · horizontal break ↔ · dot size = usage · break incl. gravity MITHRANDIR · CHARTS
PitchUsagePitchesStuff+Status
FB 42.5% 203 106 qualified
SI 37.4% 179 110 limited sample
SL 20.1% 96 102 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.
2
templated note
Home park gives the run-prevention profile a small HR cushion.
3
templated note
Primary mix entering the season: 4-Seam Fastball 41%, Sinker 33%, Slider 16%.
Live context

Current-season signal

ERA Δ-1.30
K% Δ-0.010
Sample54.3 IP

positive regression

Projection table

Point projection and range

MetricPointRangeHalf-width
Innings39.5----
Batters Faced160----
K%34.2%27.4% to 43.2%+/- 7.9%
BB%10.9%5.7% to 14.8%+/- 4.6%
Whiff%30.5%26.3% to 37.6%+/- 5.6%
HR/90.980.37 to 1.70+/- 0.67
xwOBA Against0.2810.192 to 0.336+/- 0.072
Barrel% Allowed8.3%3.3% to 12.6%+/- 4.6%
ERA3.250.91 to 5.20+/- 2.15
FIP2.851.48 to 4.17+/- 1.35
WHIP1.1910.820 to 1.548+/- 0.364
Platoon / Shape
vs LHH

657 career BF

xwOBA0.234
K%33.2%
BB%9.3%
Barrel5.3%
vs RHH

1940 career BF

xwOBA0.249
K%34.3%
BB%10.1%
Barrel7.3%