Mariners vs Astros Prediction, Odds, Moneyline, Spread & Over/Under for Sept. 21

Odds updated as of 2:11 a.m.

The Seattle Mariners will take on the Houston Astros in MLB action on Sunday.

Before checking out the MLB betting lines on FanDuel Sportsbook, we've got you covered, in terms of the vital info regarding this game.

Mariners vs Astros Game Info

• Seattle Mariners (86-69) vs. Houston Astros (84-71)
• Date: Sunday, September 21, 2025
• Time: 7:10 p.m. ET
• Venue: Daikin Park -- Houston, Texas
• Coverage: ESPN

Mariners vs Astros Odds & Moneyline

• All MLB odds, betting lines and prop bets are available on FanDuel Sportsbook.
• Moneyline: SEA: (-138) | HOU: (+118)
• Spread: SEA: -1.5 (+114) | HOU: +1.5 (-137)
• Total: 8 -- Over: (-115) | Under: (-105)

Mariners vs Astros Probable Starting Pitchers

Probable Pitchers: Logan Gilbert (Mariners) - 5-6, 3.53 ERA vs Jason Alexander (Astros) - 4-1, 4.04 ERA

This contest's pitching matchup is set, as the Mariners will send Logan Gilbert (5-6) to the mound, while Jason Alexander (4-1) will answer the bell for the Astros. When Gilbert starts, his team is 8-14-0 against the spread this season. Gilbert's team has a record of 13-5 this season when he starts and they are the favorite on the moneyline. The Astros have gone 8-3-0 against the spread when Alexander starts. The Astros were the underdog on the moneyline for five Alexander starts this season -- they won all of the games.

Mariners vs Astros Prediction & Pick

All MLB win probability predictions and picks are according to numberFire.
Prediction: Mariners win (57.6%)

Mariners vs Astros Moneyline

• Houston is a +118 underdog on the moneyline, while Seattle is a -138 favorite on the road.

Mariners vs Astros Spread

• The Mariners are favored by 1.5 runs on the road versus the Astros. The Mariners are +114 to cover the spread, while the Astros are -137.

Mariners vs Astros Over/Under

• The over/under for the Mariners versus Astros game on Sept. 21 has been set at 8, with -115 odds on the over and -105 odds on the under.

Bet on Seattle Mariners vs. Houston Astros on FanDuel today!

Mariners vs Astros Betting Trends

• The Mariners have been victorious in 62, or 59%, of the 105 contests they have been chosen as favorites in this season.
• This season Seattle has come away with a win 37 times in 57 chances when named as a favorite of at least -138 on the moneyline.
• The Mariners and their opponents have gone over the total this season in 81 of their 150 opportunities.
• The Mariners are 67-83-0 against the spread in their 150 games that had a posted line this season.
• The Astros are 32-23 in games they were the underdog on the moneyline (winning 58.2% of those games).
• Houston has a record of 12-6 in games it has played as a moneyline underdog with odds of +118 or longer (66.7%).
• The Astros have played in 154 games with a set over/under, and have combined with their opponents to go over the total 70 times (70-80-4).
• The Astros have a 77-77-0 record against the spread this season (covering 50% of the time).

Mariners Player Leaders

• Cal Raleigh leads Seattle in OBP (.361) and total hits (140) this season. He's batting .246 batting average while slugging .586.
• Among all qualified hitters in baseball, he is 96th in batting average, 19th in on-base percentage, and third in slugging.
• Julio Rodriguez has hit 31 homers this season while driving in 94 runs. He's batting .269 this season and slugging .477 with an on-base percentage of .321.
• He ranks 41st in batting average, 88th in on-base percentage and 32nd in slugging in the majors.
• Rodriguez has picked up at least one hit in two games in a row. During his last five outings he is hitting .250 with a double, a home run, two walks and three RBIs.
• Josh Naylor has collected 152 base hits, an OBP of .349 and a slugging percentage of .456 this season.
• Naylor has recorded a hit in seven straight games. In his last 10 outings he is hitting .366 with a double, two home runs, three walks and nine RBIs.
• Eugenio Suarez has 47 home runs, 113 RBI and a batting average of .230 this season.
• Suarez enters this game on a two-game hitting streak. During his last five outings he is hitting .350 with three doubles, two home runs, a walk and four RBIs.

Astros Player Leaders

• Jose Altuve has a team-high .441 slugging percentage. He's batting .263 with an on-base percentage of .323.
• Including all the qualified players in MLB, his batting average ranks 56th, his on-base percentage is 87th, and he is 62nd in slugging.
• Jeremy Pena's 150 hits, .363 OBP and .477 slugging percentage are all team-highs. He has a batting average of .304.
• His batting average is fifth among all qualified players, his on-base percentage is 16th, and he is 32nd in slugging.
• Yainer Diaz is hitting .258 with 23 doubles, a triple, 19 home runs and 20 walks.
• Carlos Correa has 27 doubles, 13 home runs and 41 walks while hitting .276.

Mariners vs Astros Head to Head

• 9/20/2025: 6-4 SEA (Favorite: Astros, Spread: -1.5, Total: 8, Favorite Moneyline: -108, Underdog Moneyline: -108)
• 9/19/2025: 4-0 SEA (Favorite: Astros, Spread: -1.5, Total: 7.5, Favorite Moneyline: -108, Underdog Moneyline: -108)
• 7/20/2025: 11-3 HOU (Favorite: Mariners, Spread: -1.5, Total: 6.5, Favorite Moneyline: -144, Underdog Moneyline: +122)
• 7/19/2025: 7-6 SEA (Favorite: Mariners, Spread: -1.5, Total: 8, Favorite Moneyline: -132, Underdog Moneyline: +112)
• 7/18/2025: 6-1 SEA (Favorite: Mariners, Spread: -1.5, Total: 7.5, Favorite Moneyline: -142, Underdog Moneyline: +120)
• 5/25/2025: 5-3 HOU (Favorite: Mariners, Spread: -1.5, Total: 8.5, Favorite Moneyline: -138, Underdog Moneyline: +118)
• 5/24/2025: 2-1 HOU (Favorite: Mariners, Spread: -1.5, Total: 7, Favorite Moneyline: -110, Underdog Moneyline: -106)
• 5/23/2025: 5-3 SEA (Favorite: Astros, Spread: -1.5, Total: 8.5, Favorite Moneyline: -116, Underdog Moneyline: -102)
• 5/22/2025: 9-2 HOU (Favorite: Mariners, Spread: -1.5, Total: 8, Favorite Moneyline: -132, Underdog Moneyline: +112)
• 4/9/2025: 7-6 SEA (Favorite: Astros, Spread: -1.5, Total: 7.5, Favorite Moneyline: -142, Underdog Moneyline: +120)

Sign up for FanDuel Sportsbook and FanDuel Daily Fantasy today!