Mithrandir Metrics
Pitcher projection 2026 Refreshed Jun 12 06:00 AM ET
Pitcher projection / STL · 2026

O'Brien, Riley

Late-inning arm with usable miss-bat shape

Primary
23.0% K%
Range
15.7% to 28.7%
Live Δ
yes
Team STL Archetype Balanced reliever 2 Age 31 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.

2026-06-12
67
Pitching
percentile
Pitching9 metrics
71
Arsenal3 metrics
57
Rolling projection

Preseason / current pace / Bayesian update

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

2026-06-12
ERA preseason3.78
ERA current pace3.95
ERA rolling p503.84
Observed weight35%
ERA
2.07 2.91 3.84 4.77 5.62
FIP
2.29 2.73 3.22 3.72 4.16
K%
19.4% 21.5% 23.9% 26.3% 28.5%
BB%
4.9% 6.5% 8.2% 9.9% 11.4%
Current percentile strip

Actual percentile with projection tick

100th = best in MLB.

2026-06-12
Pitching · percentile strip
WHIP1.21
66
ERA3.95
46
BB%5.3%
92 +58 vs proj
K%26.5%
80 +28 vs proj
xwOBA allowed0.312
51
Barrel allowed4.9%
84
Fastball velo98.3
96
Hard-hit allowed41.5%
37
Whiff%27.9%
82 +25 vs proj
Mithrandir+

Stuff+ and arsenal context

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

2026-06-12
Sinker Stuff+107
86
Mithrandir Stuff+104
71
Slider Stuff+96
15
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 57%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 O'Brien, Riley · Live snapshot series; true 50/100 PA windows require PA-level logs LG AVG 0.313 0.312 2026-06-01: 0.2912026-06-02: 0.2912026-06-03: 0.2912026-06-04: 0.3082026-06-05: 0.3142026-06-06: 0.3142026-06-07: 0.3142026-06-08: 0.3122026-06-09: 0.3122026-06-10: 0.3122026-06-11: 0.3122026-06-12: 0.312 2026-06-01 2026-06-12 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 O'Brien, Riley · Aggregate zone metrics; not pitch-by-pitch locations Edge: 38%38%Zone: 44%44%Whiff: 28%28%Called strike: 15%15%First pitch strike: 50%50%Hard hit allowed: 41%41% 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 O'Brien, Riley · 2026 arsenal snapshot Sinker: 56.5%Sweeper: 30.0%Slider: 12.6%Changeup: 0.8% SI57% · 98 mphprimary pitch SI 57%ST 30%SL 13%CH 1% MITHRANDIR · CHARTS
Mithrandir Metrics PITCH MOVEMENT Parameterized Mithrandir chart rendered as SVG for templates and exports. Pitch Arsenal O'Brien, Riley · 2026 arsenal snapshot 12″24″36″48″ Sinker: 57% usage, 1″ horizontal break, 24″ drop, 98.3 mphSI98 mphSweeper: 30% usage, 1″ horizontal break, 43″ drop, 83.7 mphST84 mphSlider: 13% usage, 2″ horizontal break, 28″ drop, 91.2 mphSL91 mphChangeup: 1% usage, 16″ horizontal break, 29″ drop, 89.9 mphCH90 mph less drop ↑ more drop ↓ · horizontal break ↔ · dot size = usage · break incl. gravity MITHRANDIR · CHARTS
PitchUsagePitchesStuff+Status
SI 57.1% 225 107 qualified
SL 42.4% 167 96 limited sample
CH 0.5% 2 76 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: Sinker 48%, Slider 30%, Sweeper 21%.
Live context

Current-season signal

ERA Δ-0.02
K% Δ+0.035
Sample30.7 IP

positive regression

Projection table

Point projection and range

MetricPointRangeHalf-width
Innings33.2----
Batters Faced144----
K%23.0%15.7% to 28.7%+/- 6.5%
BB%10.1%6.1% to 15.7%+/- 4.8%
Whiff%23.8%18.7% to 30.9%+/- 6.1%
HR/90.950.05 to 1.71+/- 0.83
xwOBA Against0.3160.239 to 0.373+/- 0.067
Barrel% Allowed5.8%1.4% to 9.3%+/- 4.0%
ERA3.971.31 to 6.13+/- 2.41
FIP3.882.74 to 5.29+/- 1.27
WHIP1.3280.985 to 1.761+/- 0.388
Platoon / Shape
vs LHH

139 career BF

xwOBA0.278
K%19.2%
BB%11.0%
Barrel3.2%
vs RHH

172 career BF

xwOBA0.273
K%18.1%
BB%8.9%
Barrel3.6%