Mariners vs. Phillies Prediction, Odds, Probable Pitchers and Prop Bets for Wednesday, Aug. 20

The Phillies are favored at home on Wednesday night.

Philadelphia Phillies outfielder Kyle Schwarber is a great prop target on Wednesday. / Bill Streicher-Imagn Images

The Seattle Mariners have squandered back-to-back chances to gain a game on the Houston Astros, losing their first two games of their series against the Philadelphia Phillies.

Luckily for Seattle, it remains just 1.5 games back of Houston after the Astros were shut out in back-to-back games by the Detroit Tigers to open the week.

On Wednesday, Seattle will play an early afternoon tilt against Philly to wrap up this three-game set, and it’s set as a road underdog once again.

Luis Castillo (3.48 ERA) will get the ball for Seattle against Phillies lefty Jesus Luzardo (4.21 ERA).

Philly has won three games in a row to get to 20 games over .500 in 2025, but can it finish the sweep this afternoon?

Let’s dive into the odds, my favorite prop bet and a prediction for this series finale. 

Mariners vs. Phillies Odds, Run Line and Total

Odds via DraftKings Sportsbook

Run Line

• Mariners +1.5 (-176)
• Phillies -1.5 (+144)

Moneyline

• Mariners: +118
• Phillies: -144

Total

• 8.5 (Over -119/Under -102)

Mariners vs. Phillies Probable Pitchers

• Seattle: Luis Castillo (8-6, 3.48 ERA)
• Philadelphia: Jesus Luzardo (11-6, 4.21 ERA)

Mariners vs. Phillies How to Watch

• Date: Wednesday, Aug. 20
• Time: 1:05 p.m. EST
• Venue: Citizens Bank Park
• How to Watch (TV): MLB Network, NBCS-PH, ROOT Sports NW
• Mariners record: 68-59
• Phillies record: 73-53

Mariners vs. Phillies Best MLB Prop Bets

Phillies Best MLB Prop Bet

• Kyle Schwarber to Hit a Home Run (+200)

Earlier today, I shared in SI Betting’s best home run props column – Daily Dinger – why Schwarber is a great bet to go deep this afternoon: 

Kyle Schwarber is tied for the National League lead in home runs entering Wednesday’s action, and he’ll look to build on that against the Seattle Mariners and Luis Castillo.

Castillo (3.48 ERA) has pitched pretty well in 2025, but he’s allowed his fair share of long balls (18 in 25 outings).

Now, he’s taking on a tough Phillies offense, and Schwarber has actually dominated against the Mariners righty in his career. The Phillies star is hitting .300 (6-for-20) with a 1.417 OPS against Castillo, homering four times against him.

Not only that, but Schwarber’s other two hits against Castillo both went for extra bases (doubles), showing that when he connects against the righty he’s really getting a hold of the ball. 

This season, Schwarber has homered 44 times and 27 of them have come against right-handed pitching, including his homer against Bryce Miller on Tuesday night. 

Mariners vs. Phillies Prediction and Pick

Both Castillo and Luzardo have put together solid 2025 seasons, but I have a hard time backing the Mariners – who have lost four in a row – on the road in this one.

Seattle is three games under .500 on the road this season, and it has not fared well against left-handed pitching, ranking 17th in MLB in batting average against southpaws.

Meanwhile, the Phillies have improved to 18 games over .500 at Citizens Bank Park in this series, and they’re 14-11 when Luzardo is on the mound in 2025. The lefty has been up and down, but in the month of August, he’s posted three consecutive quality starts with a 3.50 ERA.

Castillo, on the other hand, has failed to get through five innings in two of his three August outings, and now he’s facing one of the better lineups in MLB. 

The Phillies are ninth in MLB in batting average and 10th in OPS over the last 15 days, and I think they give Luzardo enough run support to pick up a win this afternoon. 

Pick: Phillies Moneyline (-144 at DraftKings)

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Odds refresh periodically and are subject to change.

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