The Seattle Mariners host the St. Louis Cardinals on September 9, 2025. First pitch from T-Mobile Park is scheduled for 9:40 p.m. EDT; the game will be broadcast on ROOT Sports NW.
Find my MLB betting preview and Cardinals vs Mariners prediction below, as well as probable pitchers, betting trends, injury reports and more.
My Cardinals vs Mariners Prediction
- Cardinals vs Mariners pick: Cardinals ML
My Cardinals vs Mariners best bet is on the Cardinals to win outright. Make sure to find the best odds by checking our live MLB odds page.
Cardinals vs Mariners Odds
| Cardinals Odds | ||
|---|---|---|
| Spread | Total | Moneyline |
+1.5 -120 | 7.5 -115o / -105u | +180 |
| Mariners Odds | ||
|---|---|---|
| Spread | Total | Moneyline |
-1.5 +100 | 7.5 -115o / -105u | -215 |
Cardinals vs Mariners Projected Starting Pitchers
| LHP Matthew Liberatore (STL) | Stat | RHP George Kirby (SEA) |
|---|---|---|
| 7-11 | W-L | 8-7 |
| 1.8 | fWAR (FanGraphs) | 1.9 |
| 4.15/4.60 | ERA /xERA | 4.47/4.10 |
| 3.93/4.27 | FIP / xFIP | 3.56/3.54 |
| 1.30 | WHIP | 1.23 |
| 12.6% | K-BB% | 17.7% |
| 38.8% | GB% | 43.4% |
| 96 | Stuff+ | 97 |
| 100 | Location+ | 112 |
Sean Zerillo’s Cardinals vs Mariners Prediction, Betting Analysis
George Kirby started the season with shoulder soreness, and his performance hasn’t quite rebounded to prior levels. We’re looking at career-worst metrics across the board: his strikeout-minus-walk rate is down to 18% from above 20% previously, his Stuff+ has dropped from 104 to 97, and his Pitching+ has slid from 112 to 109. His ERA has ticked up year-over-year from 3.27 to 3.68.
Over the past 30 days, the signs are even more concerning. Kirby has a 5.75 ERA, a four expected FIP, and a strikeout-minus-walk rate of just 12.4%, below the league-average benchmark of about 13.5%. I do think he’s starting to fatigue as the season goes on, and the shoulder could still be nagging him. He’s trying to grind through it as the Mariners push for the playoffs, but it’s clear he’s not at 100%.
I was able to grab the Cardinals at +200 when the rest of the market was sitting closer to +180. That price hung around late Monday night while most attention was on football. Books simply aren’t sharpening baseball markets as quickly with NFL underway, which has given us consistent closing-line value across the board.
I made this game closer to +150, so I’m comfortable betting St. Louis down to +165, and I’m expecting the line to close closer to +160.
The biggest edge here is on defense. Seattle ranks 21st in defensive runs saved and 29th in outs above average, with real weakness up the middle. Meanwhile, the Cardinals rate as the No. 1 team in outs above average and one of the better defensive clubs overall in my model. That’s a huge gap in defensive quality, and it should matter here.
Liberatore isn’t a pitcher I’m particularly high on, but he’s coming off a strong outing, and pitchers can be streaky when they get into a groove. If he can sustain that form, backed by a top-tier defense, St. Louis has real value in this spot.
Pick: Cardinals ML (+180, Fanatics; Play to +165)
Cardinals vs Mariners Betting Trends
