Mariners vs Astros Prediction 9/21/25 MLB Picks Today

In this article, we will formulate a Mariners vs Astros Prediction for this MLB game on Sunday, September 21^st at the Daikin Park in the third game of this series, with the Mariners having the 2-0 lead. Let’s take a look at the prediction for this MLB matchup.

Houston Astros Preview

The Houston Astros have an 84-71 record this season and are sitting on the second place of the AL West. The Astros have a 46-34 home record and 71-78 in over/under. They are coming off a 4-6 home defeat by the Mariners, and have back-to-back losses. They are playing the Athletics and the Angels next.

The Astros have a .252 batting average this season, .317 OBP and .398 slugging percentage. Houston’s pitching staff has a 3.85 ERA and 1.22 WHIP. Jose Altuve leads the Astros with 150 hits, adding a team-high 26 home runs. Jeremy Pena is the team’s best hitter with a .304 batting average, while Christian Walker leads the team in RBI with 82.

Jason Alexander (R) is the projected starting pitcher for the Astros, and he has a 4-1 record, 4.04 ERA and 1.30 WHIP.

Seattle Mariners Preview

The Seattle Mariners have an 86-69 record this season and are sitting on the second place of the AL West. The Mariners have a 38-42 road record and are 85-64 in over/under. They are coming off a 6-4 road victory over the Astros, and have seven consecutive wins. Over is 7-4 in their last 11 games and are playing the Rockies and the Dodgers next.

The Mariners have a .245 batting average this season, .320 OBP and .420 Slugging percentage. Seattle’s pitching staff has a 3.89 ERA and 1.23 WHIP. Julio Rodriguez leads the Mariners in hits with 170, and he is the team’s best hitter with a .269 batting average. Cal Raleigh leads the team both in RBI with 119, and in home runs with 57.

Logan Gilbert (R) is the projected starting pitcher for the Mariners, and he has a 5-6 record, 3.53 ERA and 1.05 WHIP.

Seattle Mariners @ Houston Astros Betting Trends: September 21, 2025

• Probable Starting Pitcher: Jason Alexander      Record this season: 4-1      ERA: 4.04
• Home Record: 0-1
• Last 5 against Mariners: –

Why the Houston Astros will win

• The Astros have won four of their last five games as home underdogs against the Mariners following a loss.
• The Mariners have lost six of their last eight games as road favorites against AL West opponents following a win.
• The Astros have covered the run line in eight of their last nine games following a loss.
• The Mariners have failed to cover the run line in nine of their last 11 road games against AL West opponents following a win.
• The Astros have led after 5 innings in eight of their last 10 night games.
• The Astros have led after 3 innings in eight of their last 10 night games.

• Probable Starting Pitcher: Logan Gilbert      Record this season: 5-6      ERA: 3.53
• Road Record: 2-4
• Last 5 against Astros: 2-2

Why the Seattle Mariners will win

• The favorites have won each of the Mariners’ last 13 games.
• The Astros have lost seven of their last eight games against AL West opponents following a home loss.
• The Astros have failed to cover the run line in each of their last 10 Sunday night home games.
• The favorites have covered the run line in each of the Mariners’ last seven games.
• The Mariners have led after 3 innings in each of their last five games as favorites.
• The Mariners have won the first inning in each of their last four games against AL West opponents.
• The Mariners have led after 5 innings in each of their last seven games as favorites.

Total Runs Facts

• Five of the Mariners’ last six road games against AL West opponents have gone UNDER the total runs line.
• Five of the Astros’ last six home games after playing the previous day have gone OVER the total runs line.
• The ‘Inning 1 OVER 0.5 runs’ market has hit in each of the Astros’ last seven games as home underdogs against AL West opponents.
• The ‘Inning 1 OVER 0.5 runs’ market has hit in each of the Mariners’ last five night games.

Houston Astros Player Prop Facts

• Jeremy Pena has hit a home run in two of the Astros’ last three games.
• Yordan Alvarez has recorded a Double in three of his last four appearances with the Astros as home underdogs.
• Ramon Urias has recorded at least one hit in each of his last nine home appearances against AL West opponents.
• Jeremy Pena ranks 5th amongst qualified players for Batting Average (.304) this season.

Seattle Mariners Player Prop Facts

• Julio Rodriguez has hit a home run in five of the Mariners’ last seven road games against AL opponents that held a winning record.
• Jorge Polanco has recorded at least one Double in five of the Mariners’ last six games against AL West opponents.
• Logan Gilbert has recorded a win in three of his last four road appearances against the Astros.
• Logan Gilbert has recorded seven or more strikeouts in each of his last 13 appearances with the Mariners as favorites against AL West opponents.
• Mitch Garver has recorded at least one hit in 13 of his last 14 road appearances against the Astros after playing the previous day.
• Cal Raleigh ranks 1st in the league in Home Runs (57) this season.

Matchup/League Facts

• The Astros rank 1st in the league for strikeouts this season (1447).
• The Astros rank 26th in the league for triples this season (12).
• The Mariners rank 29th in the league for doubles this season (224).
• The Mariners rank 29th in the league for triples this season (9).

Mariners vs Astros Prediction

The Mariners are 4-1 in their last 5 head-to-head meetings against the Astros, and both teams are tied 3-3 wins in their last 6 meetings in Houston. Under is 4-1 in their last 5 meetings in Houston.

In this Mariners vs Astros Prediction, the Mariners are coming as -145 road favorites. Both teams are fighting for the first place of the AL West, and the Mariners have been scorching-hot lately, with 7 straight wins. They are putting Gilbert on the mound, who has excellent this season and coming into this matchup in very good form, having a 2.54 ERA across his last 5 starts. On the flip side, Alexander has been weaker at home for the Astros, with a 4.93 ERA, and I don’t trust them to hold a red-hot Mariners squad at bay. The Mariners have a better offense to offer Gilbert run support, and I like them to get the job done on the road in this matchup.