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Early Preview Lineups: TBD Odds Posted 5 min read

Athletics vs Seattle Mariners Preview

Oakland visits Seattle at 9:40 PM ET as Luis Castillo faces Jacob Lopez. Mariners enter 10-14 with calm weather at T-Mobile Park

Athletics at Seattle Mariners MLB game preview for April 21, 2026
ATH
Athletics
Jacob Lopez LHP
@
9:40 PM ET
T-Mobile Park
SEA
Seattle Mariners
Luis Castillo RHP
Last updated Tuesday, April 21, 2026
Final This game has finished. Read the recap for final score, model grades, and box score.

Key Facts

Matchup
Athletics at Seattle Mariners
Date
Tuesday, April 21, 2026
First Pitch
9:40 PM ET
Venue
T-Mobile Park
Probable Starters
Jacob Lopez (LHP) vs Luis Castillo (RHP)
Lineups
TBD
Odds Snapshot
Apr 21, 9:41 PM ET
Last Updated
Apr 21, 6:10 PM ET

Betting Board

Snapshot Apr 21, 9:41 PM ET
Moneyline
ATH +143
SEA -154
Total
Over 8 -104
Under 8 -118
Run Line
ATH +1.5 -154
SEA -1.5 +128

Model Angles

NRFI Model
NRFI · 58%
+6.6% edge
Projected Total
TBD
Park Factor
0.95
Neutral · HR 0.92
First Pitch Weather
Roof
Climate controlled
The Athletics travel to T-Mobile Park for a Monday night clash with the Seattle Mariners, scheduled for 9:40 PM ET. Luis Castillo takes the ball for Seattle, bringing a 5.40 ERA and 1.80 WHIP into the contest while averaging 8.35 strikeouts per nine innings. Opposing him is Oakland left-hander Jacob Lopez, who enters with a 6.38 ERA, 1.96 WHIP, and 7.85 K/9 rate. The Mariners carry a 10-14 record after dropping their most recent game. Conditions at T-Mobile Park should be favorable, with temperatures around 72 degrees and calm winds at zero miles per hour. The venue plays as a slight pitcher's park with a 0.95 run factor. Seattle hopes Castillo can rebound at home while the Athletics look to capitalize on Lopez's chance to deliver in a favorable pitching environment.
  • Seattle Mariners hold a 10-14 record and lost their last game
  • Luis Castillo posts a 5.40 ERA with 1.80 WHIP this season
  • Jacob Lopez brings a 6.38 ERA and 1.96 WHIP for Oakland

Pitching Matchup

ATH Away
Jacob Lopez
LHP · 1-1 · 4 GS
ERA
6.38
WHIP
1.96
K/9
7.85
IP
18.1
Career: 4.51 ERA · 1.36 WHIP · 9.76 K/9
NRFI: 82.3%
1st Inn ERA: 2.12
SEA Home
Luis Castillo
RHP · 0-1 · 4 GS
ERA
5.40
WHIP
1.80
K/9
8.35
IP
18.1
Career: 3.58 ERA · 1.19 WHIP · 9.51 K/9

On the season, Luis Castillo holds the ERA edge in this matchup. Jacob Lopez carries a 6.38 ERA and 1.96 WHIP, while Luis Castillo sits at 5.40 ERA and 1.80 WHIP.
Strikeout rates: Jacob Lopez at 7.85 K/9, Luis Castillo at 8.35 K/9.
K projections: Jacob Lopez at 4.5 (line 5.5)
Luis Castillo projected at 5.1 (line 5.5).
Jacob Lopez has a 82.3% career NRFI rate. No first-inning data available for Luis Castillo.
This is a LHP vs RHP matchup, creating potential platoon advantages in both lineups.

Strikeout Projections

Jacob Lopez vs SEA
Proj: 4.5Line: 5.5
-1.0
Confidence:
Luis Castillo vs ATH
Proj: 5.1Line: 5.5
-0.4
Confidence:
View all K projections on SlateIQ

Our strikeout model weighs pitcher K rate, opponent lineup whiff tendency, park factors, and umpire zone size to project total strikeouts per starter.

  • Jacob Lopez (Athletics) is projected for 4.5 strikeouts against a posted line of 5.5. The projection is close to the line with no actionable edge.
  • He faces a moderate-K lineup that strikes out at 22.0% with a 28.0% whiff rate.

Luis Castillo (Seattle Mariners) is projected for 5.1 strikeouts against a posted line of 5.5. The projection is close to the line with no actionable edge.
He faces a moderate-K lineup that strikes out at 22.0% with a 28.0% whiff rate.

The Athletics lineup is more vulnerable to strikeouts in this matchup. Seattle Mariners batters K at 22.0%, Athletics batters at 22.0%.

NRFI & First 5 Analysis

NRFI Model
57.6%
probability of NRFI
+6.6%
market edge
Monitor
Market implied: 51.0%Model: 57.6%
First 5 Innings
ATH
6.38 ERA
4.5 inn/start
SEA
5.40 ERA
4.5 inn/start
F5 lean: Slight SEA
ATH K Projection
Jacob Lopez
4.5proj
Line: 5.5
-1.0 NEUTRAL
Confidence
SEA K Projection
Luis Castillo
5.1proj
Line: 5.5
-0.4 NEUTRAL
Confidence
Explore all model projections

Our NRFI model analyzes both starting pitchers' first-inning profiles, the top-of-order hitters in each lineup, the umpire's historical zone, and environmental factors to produce a probability estimate. For this game, the model assigns a 57.6% probability of no runs in the first inning, compared to the market's implied probability of 51.0%.

  • That creates a moderate 6.6% edge on NRFI.
  • The best available line is NRFI -104 / YRFI -118 at FanDuel.
  • Home plate umpire Malachi Moore runs a average zone. See the umpire section below for full career data.
  • Our NRFI model sits at 17-23 (42.5%) on official picks this season.

Prop Edges

3 model signals detected
Home Run Elite 0.5
23.2%
Home Run Very Strong 0.5
14.9%
Home Run Very Strong 0.5
14.4%
See all today's picks and edges

Lineup & Matchup Breakdown

Athletics Projected
Projected batting order unavailable. This will update when probable or confirmed lineup data is available.
Seattle Mariners Projected
Projected batting order unavailable. This will update when probable or confirmed lineup data is available.
Batter vs Pitcher matchup tool

Lineups are unavailable as of this writing.

Ballpark, Weather & Umpire

T-Mobile Park
Run Factor0.95
HR Factor0.92
Full park profile
Home Plate Umpire
Malachi Moore
Average NRFI: 38.6% 88 games
Full umpire profile
  • T-Mobile Park carries a 0.95 run factor (neutral).
  • Home run factor: 0.92 — the park suppresses HR power.
  • Park notes: Cool maritime climate; Lower wall in right field; Retractable roof.
  • Roof: Retractable.

Climate controlled. Roof expected closed. Standard 72F conditions, no wind factor.

  • Home plate umpire: Malachi Moore.
  • Career NRFI rate: 38.6% across 88 games tracked.
  • Zone tendency: Average.
  • K factor: 1.016 (league average strikeouts in his games).

Run Projections & Total

Run projections not available for this game.

The Bottom Line
Castillo and Lopez both carry elevated ERAs and WHIPs into this interleague showdown. T-Mobile Park's pitcher-friendly 0.95 run factor and ideal weather conditions could help both starters. The Mariners aim to bounce back after their latest loss.
This preview is generated from thecapper.io projection models and publicly available data. All projections are model estimates, not guarantees. Gamble responsibly. If you or someone you know has a gambling problem, call 1-800-GAMBLER.