Seattle Mariners vs. Kansas City Royals Picks and Prediction for Thursday, September 18, 2025
In the closing game of a three-game American League series, the Seattle Mariners are taking on the Kansas City Royals inside Kauffman Stadium on Thursday afternoon in our Mariners vs. Royals prediction. This article is being written before Wednesday’s game. The Mariners are first in the AL West with an 83-68 record and are sending right-hander Luis Castillo to the mound. The Padres are third in the AL Central with a 75-76 record and have righty Stephen Kolek getting the ball. Today’s edge: MLB predictions for Seattle Mariners at Kansas City Royals built on form and matchups.
Mariners Looking to Win AL West
The Seattle Mariners are looking to continue dominating after their 12-5 road win over the Kansas City Royals on Tuesday. The lineup was able to go 14-for-40 with four walks and five strikeouts on the day. Dominic Canzone (x3) and Cal Raleigh (x2) hit home runs while Leo Rivas stole a base. The Mariners went 3-for-13 with runners in scoring position and stranded six men on base. Logan Gilbert pitched well in a win as he allowed a pair of runs in 5.2 innings.
The Mariners are sending right-hander Luis Castillo to pitch and he is stepping up as in 30 starts, he is 9-8 in 167.1 innings with a 3.76 ERA and a 1.25 WHIP. He has been struggling a bit with the ability to keep the ball in the park, as he allowed 22 home runs after giving up 25 in 175.1 innings last year. Castillo lost in his only start against the Royals this season as he pitched five innings and gave up five runs on six hits with one walk and four strikeouts.
Injury Report for Seattle
- Pitcher Jackson Kowar: Shoulder (OUT)
- Pitcher Trent Thornton: Achilles (OUT)
- Pitcher Logan Evans: Elbow (OUT)
- Pitcher Gregory Santos: Knee (OUT)
- Second baseman Ryan Bliss: Biceps (OUT)
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Royals Fighting for Last AL Wild Card Spot
The Kansas City Royals are looking to recover after Tuesday’s 12-5 home loss against the Seattle Mariners in their most recent game. The Royals were able to go 9-for-37 with three walks and six strikeouts at the plate as Carter Jensen hit a pair of home runs. Kansas City finished 1-for-7 with runners in scoring position while leaving 10 men on base. Michael Wacha struggled in a loss as he gave up seven runs in 2.2 innings of work.
Right-hander Stephen Kolek is going to be taking the mound for the Kansas City Royals in this game and has been doing well as he is 5-5 with a 3.71 ERA and a 1.20 WHIP in 99.1 innings over 17 starts. He has been doing a good job in terms of limiting the amount of hits as he has allowed a .246 batting average against this year. Kolek faced the Mariners once this season as a member of the San Diego Padres, where he threw five innings and gave up five runs on eight hits with one walk and four strikeouts.
Injury Report for Kansas City
- Pitcher Seth Lugo: Back (OUT)
- Pitcher Bailey Falter: Biceps (OUT)
- Pitcher Hunter Harvey: Abductor (OUT)
- Pitcher Steven Cruz: Shoulder (OUT)
- Pitcher Kris Bubic: Rotator Cuff (OUT)
- Pitcher Alec Marsh: Shoulder (OUT)
- Pitcher James McArthur: Elbow (OUT)
Mariners vs. Royals Pick
Spread Pick for Mariners vs. Royals
- Seattle Mariners ML (4 units)
These pitchers are pitching at a bit of different levels during an extended period as Luis Castillo is 5-3 with a 4.17 ERA and a 1.27 WHIP in 82.0 innings (15 starts), while Stephen Kolek is 2-5 with a 5.10 ERA and a 1.39 WHIP in 65.1 innings (12 starts). The ability to hit with runners in scoring position shows there is a difference offensively here as the Mariners are 18th in MLB with a .742 team OPS in those at-bats, while the Royals are 25th with a .696 team OPS with runners in scoring position this season. Seattle is 3-2 in their five games against Kansas City so go with the Seattle Mariners to record a victory once again.
Over/Under Pick for Seattle Mariners vs. Kansas City Royals
- Over (5 units)
The road/home splits for these starting pitchers show a lot of struggles as Luis Castillo is 5-4 with a 5.09 ERA and a .314 batting average against in 74.1 innings (14 road starts) while Stephen Kolek is 2-3 with a 6.55 ERA and a 1.33 WHIP in 33.0 innings (six home starts) entering this game. Since the All-Star break, these teams have been hitting well as the Mariners are tied with the Chicago White Sox for 10th place with a .734 team OPS ,while the Royals are ninth with a .737 team OPS since then. The over has hit in six of their last eight games against each other, so take the over to hit as well.
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