Seattle Mariners vs. Kansas City Royals Prediction and Picks for Tuesday, September 16th, 2025
The MLB action continues on Tuesday with an American League matchup between the Seattle Mariners (82-68) and the Kansas City Royals (72-75). We’ve got you covered with our Mariners vs. Royals prediction. Below, I’ll dive into each team’s recent form and break down the starting pitching matchup, before concluding with picks and predictions on this contest that gets underway at 7:40 ET from Kauffman Stadium in Kansas City, MO. Read on for free MLB picks on this game, and check out that link for other game breakdowns.
Mariners Sit Atop the A.L. West
The American League West has been a rollercoaster ride this season, but the Seattle Mariners are catching fire and making a push for the divisional title. The M’s have won nine straight games, which has catapulted them up the standings and into first place in the West. They’re now 82-68, holding a 1.0-game edge over the second-place Astros. From a sports betting perspective, Seattle is -180 to win the West, while sitting at +950 to win the World Series. The Mariners are riding a nine-game winning streak, and they’re coming off of a weekend sweep of the Angels (7-6, 2-1, 5-3, 11-2) at home.
It was none other than Cal Raleigh leading the way offensively in Seattle’s 11-2 win on Sunday, going 2-for-4 and blasting his league-leading 54th home run. George Kirby (6.1 IP, 2 ER) was sharp in his start and earned the win.
- Logan Gilbert gets the nod for Tuesday’s series opener, and the 28-year-old has been serviceable, but not overpowering in 2025.
- In 22 starts (114.1 IP), the right-hander has gone 4-6 with a 3.54 ERA and a 1.03 WHIP.
- Gilbert last pitched on Wednesday against the Cardinals, and he held them to one earned run on five hits and a walk over 4.2 innings.
- It was a no-decision effort in a 4-2 victory.
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Royals Sliding Out of Contention
Meanwhile, the vibes aren’t too high for the Kansas City Royals right now. The organization was coming off of an ALDS appearance in 2024, but their chances of making it back to the postseason are looking slimmer by the day. The Royals enter the new week sitting at 75-75, which puts them 6.5 games out of the wild card. Kansas City is just 2-6 in its last eight games, and the team is coming off of a series loss to Philadelphia (L: 8-2, L: 8-6, W: 10-3).
The Royals salvaged a win over the Phillies on Sunday, hammering them 10-3. Salvador Perez stole the show offensively, going 2-for-5 with a home run and five RBI. Noah Cameron (7.0 IP, 2 ER) turned in a quality start and picked up the win.
- Michael Wacha will toe the rubber for the Royals on Tuesday, and he’s coming off of the 7-day IL after sustaining a concussion in an off-field incident.
- The right-hander has looked great this year, going 9-11 with a 3.45 ERA (21st) and a 1.18 WHIP (20th).
- Most recently, Wacha faced the Twins on September 5th, holding them to one earned run on four hits and two walks over 5.2 innings.
- It was a winning effort in the 2-1 victory.
Mariners vs. Royals Pick
Moneyline Pick for Mariners vs. Royals
- Seattle Mariners Moneyline (-135) (5 units)
These teams are on opposite trajectories heading into the new week. The Mariners are in the midst of a 9-0 SU heater, and I’m going to ride with them against this Royals squad that’s just 2-6 SU in its last eight games.
I do expect runs to be at a premium in this game, but I think we’ll see Seattle’s offense do enough to secure the win. Their current roster has seen Michael Wacha well, slashing .301/.346/.538 against him over 143 at-bats. Furthermore, Wacha has conceded at least three earned runs in two out of his last three starts. If Seattle can scratch across three or four runs on Tuesday, it’ll likely be enough to keep them in contention to win the game. Give me the M’s on the moneyline.
Over/Under Pick for Mariners vs. Royals
- Under 8.5 (-115) (5 units)
Even though the Mariners are on a magical nine-game winning streak, they haven’t really been pulverizing the baseball offensively. Over the last seven days, Seattle is a modest 14th in wOBA (.321) and 11th in ISO (.171). They’re running into Wacha, who has been sharp at home this season with a 2.92 ERA.
On the other hand, Logan Gilbert is finally finding his fantastic form that we’ve seen in recent years. He owns a 2.38 ERA across his last four starts (22.2 IP). Kansas City’s current roster is slashing just .235/.303/.457 against him over 81 at-bats. Over the last seven days, the Royals are just 24th in wOBA (.274) and 23rd in ISO (.128). I’ll gladly play the under while it’s sitting as high as 8.5.
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