T-Mobile Park in Seattle hosts the series finale of this three-game set at 4:10 PM ET as the Chicago Cubs (74-56) visit the Seattle Mariners (62-68). The Mariners won Friday's opener 6-5 in 10 innings on a walk-off single before taking Game 2 on Saturday, giving Seattle a surprising two-game sweep of one of baseball's better teams heading into Sunday's rubber match. The Cubs will counter with Shota Imanaga (8-9, 3.77 ERA), while Seattle hands the ball to Bryce Miller (4-7, 3.71 ERA). Miller and his team have a record of 1-13-0 against the spread when he starts. The Cubs are mashing the ball, posting a 116 wRC+ and .218 ISO over the last 14 days, while Seattle's bullpen has melted down recently, posting a 7.59 ERA and 1.64 WHIP. Read on to find out who takes the series finale in our Cubs vs. Mariners prediction. Don't go down on strikes! Get our top MLB Predictions and increase your bankroll!
Imanaga Gives Chicago Their Best Sunday Arm
Shota Imanaga carries an 8-9 record and 3.77 ERA into Sunday's series finale. The Cubs are 10-14-0 ATS in Imanaga's 24 starts and have a 2-1 record in his three starts this season when they were the underdog on the moneyline. The Japanese left-hander's combination of a four-seam fastball, a devastating splitter, and an elite changeup gives him the three-pitch arsenal that generates the weak contact profile that T-Mobile Park's run-suppressive environment amplifies to its fullest.
Imanaga gives Chicago the stability needed to keep the Mariners' lineup in check and exploit Seattle's pitching struggles at plus-money. The Seattle lineup has hit just .214 with a .288 wOBA against left-handed pitching over the last month, a platoon split that specifically benefits a left-hander with Imanaga's swing-and-miss capacity. Pete Crow-Armstrong has put up an on-base percentage of .377, a slugging percentage of .554, and has 138 hits, all club-highs for the Cubs, while batting .279. Alex Bregman is hitting .258 with 24 doubles, a triple, 19 home runs and 63 walks. Seiya Suzuki is batting .267 with 24 doubles, 22 home runs and 58 walks. The Cubs lead the majors in OPS, ISO, and slot second in wOBA over the last 14 days, an offensive surge that gives Imanaga the run-support ceiling that his ERA profile has historically required.
Chicago has hit the moneyline in 21 of the last 30 away games, a road-game money-line conversion rate that reflects a team confident enough in its talent to win in any environment. The Cubs' 24-13 record when facing left-handed starters this season is the one context where their offensive superiority is least relevant Sunday, but Imanaga's platoon advantage against a Seattle lineup that hits poorly against lefties makes it the right day to trust the Cubs' overall quality rather than the specific lefty-on-lefty context.
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Miller Is 1-13 ATS
Bryce Miller carries a 4-7 record and 3.71 ERA into Sunday's assignment. His team has a record of 1-13-0 against the spread when he starts, one of the worst individual ATS records of any starter in the American League. Miller's team has a record of 3-9 this season when he starts and they are the favorite on the moneyline. That 1-13 ATS record is the most alarming single-pitcher spread performance indicator on Sunday's board, a starter whose team consistently underperforms the expected margin regardless of the opposing lineup or game environment.
Miller's 2026 home splits across 12 starts: 3-4, 3.13 ERA (69 IP, 24 ER), 1.04 WHIP, 57 H, 8 HR, 15 BB, 71 K. His career versus the Cubs covers two starts: 0-2, 9.90 ERA (10 IP, 11 ER), 1.30 WHIP. A 9.90 career ERA in two previous starts against this specific Cubs lineup is the individual head-to-head data point that makes Miller's assignment Sunday more fraught than his overall 3.71 ERA would suggest, and a Cubs lineup posting a 116 wRC+ over the last 14 days is the specific hot-bat context that career-versus matchup data most reliably predicts.
Seattle's bullpen has melted down recently, posting a 7.59 ERA and 1.64 WHIP, a relief corps collapse that removes the late-inning safety net that T-Mobile Park's run-suppression environment typically provides once the starter exits. Even if Miller gives Seattle five quality innings, the Cubs have demonstrated throughout this road trip that they generate offense in the middle innings against bullpens under organizational strain.
Cubs vs. Mariners Picks
- Money Line Pick: Chicago Cubs
Imanaga gives Chicago the stability needed to keep the Mariners' lineup in check and exploit Seattle's pitching struggles at plus-money. The Cubs have hit the moneyline in 21 of their last 30 away games, Imanaga's platoon advantage against Seattle's left-handed-pitching struggles is genuine, and Miller's 9.90 career ERA against this specific Cubs lineup is the individual data point that makes Sunday's matchup more favorable for Chicago than the surface numbers imply. Miller's team has a record of 1-13-0 against the spread when he starts, the single most alarming indicator available heading into Sunday's finale. Take the Cubs.
- Over/Under Pick: Under 7.5 Runs
Imanaga's run-suppression quality at T-Mobile Park, where his splitter and changeup generate the ground-ball contact that the marine layer and deep outfield amplify, is the primary Under driver from the Cubs' side of the ledger. Miller's 3.13 home ERA and 1.04 home WHIP this season represent genuine quality-start capacity against a Cubs lineup that has been rolling, but even the hotter offensive unit in baseball will struggle to generate the volume needed to clear 7.5 against a pitcher who has been excellent at home in 2026. The total opened at 7.5 and has held firm — a stable number that reflects market respect for both starters' ability to keep the game tight through six innings. Take the Under 7.5 and back T-Mobile Park to produce the contained, low-scoring finale that the series' first two tight games have already previewed.
