The Seattle Mariners host the Houston Astros on July 18, 2025. First pitch from T-Mobile Park is scheduled for 10:10 p.m. ET; the game will be broadcast on SCHN.
The Astros will hand the ball to Brandon Walter coming out of the All-Star break, and the Mariners' Luis Castillo will oppose him.
Find my MLB betting preview and Astros vs Mariners prediction below, as well as probable pitchers, betting trends, injury reports and more.
My Astros vs Mariners Prediction
- Astros vs Mariners picks: Under 7.5
My Astros vs Mariners best bet is on the under. Make sure to find the best odds by checking our live MLB odds page.
Astros vs Mariners Odds
| Astros Odds | ||
|---|---|---|
| Spread | Total | Moneyline |
+1.5 -190 | 7.5 -110o / -110u | +115 |
| Mariners Odds | ||
|---|---|---|
| Spread | Total | Moneyline |
-1.5 +154 | 7.5 -110o / -110u | -135 |
Astros vs Mariners Projected Starting Pitchers
| LHP Brandon Walter (HOU) | Stat | RHP Luis Castillo (SEA) |
|---|---|---|
| 1-2 | W-L | 6-5 |
| 0.6 | fWAR (FanGraphs) | 1.5 |
| 3.98 / 2.92 | ERA / xERA | 3.41 / 4.45 |
| 4.04 / 2.91 | FIP / xFIP | 3.83 / 4.17 |
| 1.01 | WHIP | 1.24 |
| 23.0 | K-BB% | 13.1 |
| 47.9 | GB% | 41.1 |
| 97 | Stuff+ | 99 |
| 106 | Location+ | 104 |
Alex Hinton’s Astros vs Mariners Preview
Houston Astros Betting Preview: Expect Quality Start From Walter
The Houston Astros have made the playoffs in eight straight seasons and nine of the last 10 years. However, they have an argument for being one of the MLB's biggest surprises in 2025.
Gone is Kyle Tucker, who just made his fourth All-Star appearance on Tuesday night and was wearing a Cubs uniform.
Houston has also missed slugger Yordan Alvarez for the majority of the first half, and there's no timetable for his return.
Without Tucker and Alvarez, Houston is missing 58 home runs and over 10 WAR from last year's team. Yet, the Astros have the second-best record in the American League and begin the second half with a five-game lead over the Mariners in the AL West.
Six Astros have already cracked double digits in home runs, led by Isaac Paredes, who was acquired in the Tucker trade, and team mainstay Jose Altuve.
Jeremy Pena leads them with 4.6 WAR this season. He's missed the last few weeks with a rib injury and will be out of the lineup again tonight. However, his return appears to be imminent.
The Astros lead the MLB in team batting average, but they're tied for 15th in runs scored.
A strong pitching staff has carried the way, as they rank fifth in the MLB with a 3.61 team ERA. Framber Valdez and Hunter Brown have anchored the rotation this season. Both have sub-2.80 ERAs and are a combined 19-7 this season.
Tonight, they'll look to begin the second half with a quality start from Walter. The 28-year-old took a hard-luck decision in his final outing before the break. He struck out seven in six innings, and the only hits allowed were two solo home runs as the Astros fell 4-2 to the Guardians.
Walter has a 3.98 ERA in 40 2/3 innings with 40 strikeouts against just two walks this season. He'll be making his first career appearance against the Mariners tonight.
Seattle Mariners Betting Preview: Worse Home Splits for Offense
Despite blowing a 5-0 lead to the Yankees, the Mariners were still able to finish the first half on a high note. They went to Detroit and ambushed the Tigers for 35 runs in the three-game sweep.
Cal Raleigh homered twice last Friday and finished the first half with 38 home runs, one shy of Barry Bonds' record for homers before the All-Star break. However, he did break Ken Griffey Jr.'s Mariners mark and already set a new career high.
Raleigh is on pace for 64 home runs this season, but he only needs 12 to become the first primary catcher with 50 home runs in a season. He's second in AL MVP odds behind Aaron Judge and has been the primary reason why the Mariners hold the final AL wild card spot.
Lately, he's had some help. Randy Arozarena has nine of his 17 home runs on the year since June 30. Julio Rodriguez homered in all three games in Detroit and finished the first half with 14 four-baggers, 17 stolen bases and a 3.9 WAR.
While Rodriguez didn't participate, the two outfielders joined Raleigh on the AL All-Star team.
J.P. Crawford may not have been looking forward to the All-Star break. He closed the first half on a 14-game hitting streak and has hit .345 with seven runs scored and seven RBI in that span.
The Mariners are eighth in the MLB in runs scored. However, they're averaging over a run game per game less at T-Mobile Park, and they're hitting .226 at home this season.
Their strong rotation usually carries the way for them, and they'll begin the second half by handing the ball to long-time ace Castillo.
Over the last few years, Castillo's strikeouts have been declining. This year, he also has a .268 xBA and a 4.45 xERA. Yet, he's been able to work out of trouble this season and has a 3.41 ERA on the year.
He's 2-2 with a 3.42 ERA in eight career starts against the Astros.
Astros vs Mariners Prediction, Betting Analysis
The under is 5-3-2 in their last 10 meetings, including two of the three games in Seattle in April. One of those games was a 2-1 extra-inning Astros victory in which Castillo started. He went five scoreless innings in that outing, and he has a 2.29 ERA at home this season.
While his battery mate, Raleigh, will go for 40 home runs this weekend, the Mariners are averaging just 3.9 runs per game at home.
Walter has been solid this season, and he'll be backed by a strong Astros bullpen that's third in bullpen ERA.
If the bats are a bit slow to wake up coming out of the break, that could result in a low-scoring game.
Pick: Under 7.5 (-110, BetMGM)
Moneyline
I have no play on the moneyline.
Run Line (Spread)
I'm not interested in the spread tonight.
Over/Under
As mentioned, I recommend the under for this game.
