Mariners vs. Phillies Prediction, Odds & Best Bets: Seattle to Take Advantage of Suarez’s Struggles

Can Seattle pick up a big win over Philadelphia as it continues to vie for an AL Wild Card berth?

Mike Spector

Last Updated: August 18, 2025 8:03 AM EDT • 3 minute read

Mariners vs. Phillies Prediction, Odds & Best Bets: Monday, Aug. 18 — Pictured: Philadelphia Phillies starting pitcher Ranger Suarez walks off the field as we make our best Mariners vs. Phillies prediction. Photo by Katie Stratman via Imagn Images.

The Seattle Mariners are amid an interesting scheduling quirk, playing in their third city in three days, as they begin a three-game series with the Philadelphia Phillies from Citizens Bank Park (6:45 p.m. ET, MLBN). Our Mariners vs. Phillies prediction backs Seattle at -108 moneyline odds at the best sports betting sites despite the scheduling disadvantage.

Philadelphia is trotting out one of its worst starting pitchers in Ranger Suarez, and his struggles are a focus of my Mariners vs. Phillies best bets.

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✅ Mariners vs. Phillies prediction: Mariners to win (-108 via FanDuel)

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If Philadelphia had anyone but Suarez toeing the rubber, I would have said Seattle’s constant travel and all of the distractions it had with the Little League Classic would be too much to overcome. But Suarez’s struggles and Seattle’s success against southpaws have me backing the visitors in my Mariners vs. Phillies prediction.

Seattle is 20-12 against left-handed starting pitchers, and is one of three MLB teams eight games above .500 or better in that split. Meanwhile, Suarez has allowed 24 runs over his last six starts. He is 1-4 with a 6.11 ERA over that span, after allowing just 18 runs in his previous 12 starts.

Suarez’s history of second-half struggles is the biggest reason for my Mariners vs. Phillies best bet. Over the last two seasons, the lefty has pitched to a 2.50 ERA in 32 starts compared to a 6.06 ERA in 13 combined starts after the All-Star break. Perhaps Suarez is ailing, as his fastball the first time through the order in his last start was two mph slower than his season average.

Using a FanDuel promo code you can get this game as a virtual pick ’em with each team at -108 odds, as all other competing best sportsbooks have Seattle as slight -115 moneyline favorites.

💰 Best Mariners vs. Phillies player prop

✅ Best Mariners vs. Phillies player prop: Julio Rodriguez Over 0.5 RBIs (+180 via DraftKings)

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Rodriguez has 22 RBIs against left-handed pitchers, which ranks second on the team behind Cal Raleigh. His numbers against southpaws have improved mightily over the last 30 days, which is why I am backing him to drive in a run as my best Mariners vs. Phillies player prop.

Rodriguez is batting .252 with a .519 slugging percentage against left-handed pitchers this season. But over the last 30 days, he has improved those numbers to .273 and .636, respectively.

Rodriguez leads the team with a 158 wRC+ against southpaws over the last month, and should again have plenty of RBI chances hitting behind Raleigh and Randy Arozarena.

These are great odds for a hitter who has four RBIs over his previous four games. A $10 winning wager would earn maximum value by using a DraftKings promo code (net $18 in profits), compared to the $16.50 one would stand to earn based on the +165 odds at the low end of the market.

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Written by:
Mike Spector

Mike started in the sports writing industry in July 2019, and gained a lot of followers in his first year after finishing with the No. 2 overall record in an annual NFL betting competition, which made picks against the spread, and from an Over/Under and moneyline perspective. Mike is an avid fan of the NFL, MLB, tennis, and all college sports. In his opinion, March Madness is the best sporting event there is, and he's especially euphoric starting with conference tournament time in college basketball. Mike's a big advocate of "fading the public" and making plays that are contrarian, constantly citing that "there are reasons why they have those big shiny buildings in Las Vegas." When making wagers, Mike always scours the best odds at all of the major sports betting sites, where he mostly sifts through DraftKings, FanDuel, BetMGM, and bet365. He's tried several others and is of the firm belief that bettors should not just stick to one sportsbook, as there is always likely better value to be had with the same wager. In addition, while Mike received his undergraduate degree from Villanova University, he has no issue betting against the Wildcats when it comes to college basketball wagering, and suggests other bettors should always put their “head” before their “hearts.”