The Kansas City Royals host the Seattle Mariners on September 18, 2025. First pitch from Kauffman Stadium is scheduled for 2:10 p.m. EDT; the game will be broadcast on ROOT Sports NW.
Find my MLB betting preview and Mariners vs Royals prediction below, as well as probable pitchers, betting trends, injury reports and more.
My Mariners vs Royals Prediction
- Mariners vs Royals picks: Under 9
My Mariners vs Royals best bet is Under 9. Make sure to find the best odds by checking our live MLB odds page.
Mariners vs Royals Odds
| Mariners Odds | ||
|---|---|---|
| Spread | Total | Moneyline |
-1.5 +129 | 9 -121o / -100u | -121 |
| Royals Odds | ||
|---|---|---|
| Spread | Total | Moneyline |
+1.5 -157 | 9 -121o / -100u | +102 |
Mariners vs Royals Projected Starting Pitchers
| RHP Luis Castillo (SEA) | Stat | RHP Stephen Kolek (KCR) |
|---|---|---|
| 9-8 | W-L | 5-5 |
| 2.2 | fWAR (FanGraphs) | 1.4 |
| 3.76 / 4.31 | ERA /xERA | 3.71 / 4.41 |
| 4.03 / 4.13 | FIP / xFIP | 3.90 / 4.26 |
| 1.25 | WHIP | 1.20 |
| 14.7% | K-BB% | 9.5% |
| 42.5% | GB% | 51.0% |
| 96 | Stuff+ | 95 |
| 105 | Location+ | 100 |
Mariners vs Royals Prediction, Betting Analysis
This system bets the under in daytime games where solid visiting arms suppress scoring and the home offense is steady but not explosive: Day games often play slower due to sun, shadows, and shorter rest.
Visitor SP filters identify efficient pitchers capable of limiting damage without elite notoriety.
Home team hit rate between 7.81 and 8.24 ensures average offensive output—enough to avoid “over” volatility but not dominate.
The regular season only avoids erratic postseason scoring.
Combined with lower totals and calm game tempos, this approach isolates a pocket where public expectations may overshoot actual output.
Pick: Under 9
