St. Louis Cardinals vs Seattle Mariners Prediction, Odds and Picks for Tuesday, 09/09/25

The St. Louis Cardinals will send left hander Matthew Liberatore to the mound, and he’s shown steady progress in his first full season as a starter. Through 26 outings, Liberatore carries a 4.15 ERA and 1.30 WHIP with 109 strikeouts in 136 innings, while underlying numbers like a 3.69 FIP suggest he’s been more effective than his surface stats indicate. His ability to mix in a quality changeup alongside a developing fastball/slider combination has allowed him to limit damage early in games, often working through lineups twice before trouble sets in. Against a Mariners team that has been prone to inconsistency at the plate, particularly versus left handed pitching, Liberatore should be in position to keep the game tight in the early frames.

The Seattle Mariners counter with George Kirby, a command first righty who remains one of the better strike throwers in the league. Across 19 starts, Kirby has posted a 4.47 ERA and 1.23 WHIP with 104 strikeouts in 104.2 innings. While his overall numbers are higher than in previous seasons, advanced metrics like a 3.56 FIP and low walk rate highlight his ability to control games when he’s locating effectively. He will look to set the tone against a Cardinals lineup that has produced runs in bursts but remains inconsistent against quality pitching. With Liberatore showing improvement and Kirby capable of navigating opposing hitters with his precision, both starters should find success early. That combination makes the First 5 Innings under the most appealing angle, as this matchup projects as a pitcher’s duel through the early innings.

Cardinals vs Mariners Prediction: F5 Under 4.5 (-115) available at time of publishing. Playable to -135

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