Mariners vs Reds Prediction, Odds, Moneyline, Spread & Over/Under for July 21

Odds updated as of 10:12 a.m.

On Tuesday in MLB, the Seattle Mariners are up against the Cincinnati Reds.

Before you do any MLB betting on this game at FanDuel Sportsbook, here's everything you need to know.

Mariners vs Reds Game Info

• Seattle Mariners (51-50) vs. Cincinnati Reds (45-54)
• Date: Tuesday, July 21, 2026
• Time: 9:40 p.m. ET
• Venue: T-Mobile Park -- Seattle, Washington
• Coverage: Mariners.TV and Reds.TV

Mariners vs Reds Odds & Moneyline

• All MLB odds, betting lines and prop bets are available on FanDuel Sportsbook.
• Moneyline: SEA: (-112) | CIN: (-104)
• Spread: SEA: +1.5 (-192) | CIN: -1.5 (+158)
• Total: 7.5 -- Over: (-105) | Under: (-115)

Mariners vs Reds Probable Starting Pitchers

Probable Pitchers: Luis Castillo (Mariners) - 3-8, 4.93 ERA vs Chase Burns (Reds) - 11-1, 2.54 ERA

This contest's pitching matchup is set, as the Mariners will send Luis Castillo (3-8) to the mound, while Chase Burns (11-1) will get the nod for the Reds. When Castillo starts, his team is 4-11-0 against the spread this season. Castillo's team has a record of 3-6 this season when he starts and they are the favorite on the moneyline. The Reds have a 14-4-0 record against the spread in Burns' starts. The Reds have a 4-1 record in Burns' five starts this season when they were the moneyline underdog.

Mariners vs Reds Prediction & Pick

All MLB win probability predictions and picks are according to numberFire.
Prediction: Mariners win (61%)

Mariners vs Reds Moneyline

• The moneyline numbers for Mariners vs. Reds reveal Seattle as the favorite (-112) and Cincinnati as the underdog (-104) on the road.

Mariners vs Reds Spread

• The Reds are 1.5-run favorites against the spread for this matchup with the Mariners. The Reds are +158 to cover, while the Mariners are -192 to cover as a 1.5-run underdog on the runline.

Mariners vs Reds Over/Under

• Mariners versus Reds on July 21 has an over/under of 7.5 runs, with the odds on the over -105 and the under set at -115.

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Mariners vs Reds Betting Trends

• The Mariners have come away with 46 wins in the 85 contests they have been listed as the favorites in this season.
• This year Seattle has won 46 of 84 games when listed as at least -112 on the moneyline.
• The Mariners and their opponents have hit the over in 48 of their 100 games with a total set by oddsmakers this season.
• The Mariners are 37-63-0 against the spread in their 100 games with a line set by sportsbooks this season.
• The Reds have won 44.6% of the games this season they were the underdog on the moneyline (29-36).
• Cincinnati is 24-35 (winning 40.7% of its games) when it has played as a moneyline underdog of -104 or longer.
• In the 97 games oddsmakers have set an over/under for the Reds, they have combined with opponents to go over the total 55 times (55-41-1).
• The Reds have covered 53.6% of their games this season, going 52-45-0 ATS.

Mariners Player Leaders

• Randy Arozarena leads Seattle with 96 hits and an OBP of .381, plus a team-best slugging percentage of .450. He's batting .284.
• Among qualified hitters in the majors, he is 26th in batting average, 13th in on-base percentage, and 58th in slugging.
• Arozarena will look for his third straight game with a hit in this contest. In his last five games he is batting .222 with a home run, a walk and three RBIs.
• Josh Naylor is batting .253 with 12 doubles, eight home runs and 31 walks, while slugging .351 with an on-base percentage of .317.
• His batting average ranks 79th among qualified players, his on-base percentage 95th, and his slugging percentage 134th.
• Naylor takes a two-game streak with at least one hit into this one. In his last five games he is hitting .278 with two walks and an RBI.
• Cole Young has 92 hits this season and has a slash line of .254/.314/.406.
• Julio Rodriguez has been key for Seattle with 91 hits, an OBP of .320 plus a slugging percentage of .417.
• Rodriguez brings a two-game hitting streak into this game. In his last five games he is hitting .313 with two walks and two RBIs.

Reds Player Leaders

• Sal Stewart has a slugging percentage of .470, a team-high for the Reds. He's batting .251 with an on-base percentage of .331.
• Including all qualifying players in the majors, he ranks 81st in batting average, 76th in on-base percentage and 43rd in slugging percentage.
• Elly De La Cruz paces his team with 89 hits and a .352 on-base percentage. He has a batting average of .279 while slugging .502.
• Including all qualifying hitters, he ranks 37th in batting average, 45th in on-base percentage and 21st in slugging percentage.
• Spencer Steer is hitting .245 with 14 doubles, 16 home runs and 34 walks.
• JJ Bleday is hitting .239 with 11 doubles, a triple, 16 home runs and 41 walks.

Mariners vs Reds Head to Head

• 7/20/2026: 8-0 SEA (Favorite: Mariners, Spread: -1.5, Total: 7.5, Favorite Moneyline: -146, Underdog Moneyline: +124)
• 4/17/2025: 11-7 SEA (Favorite: Reds, Spread: -1.5, Total: 8.5, Favorite Moneyline: -130, Underdog Moneyline: +110)
• 4/16/2025: 5-3 SEA (Favorite: Mariners, Spread: -1.5, Total: 8.5, Favorite Moneyline: -112, Underdog Moneyline: -104)
• 4/15/2025: 8-4 CIN (Favorite: Mariners, Spread: -1.5, Total: 8.5, Favorite Moneyline: -112, Underdog Moneyline: -104)
• 4/17/2024: 5-1 SEA (Favorite: Mariners, Spread: -1.5, Total: 7.5, Favorite Moneyline: -130, Underdog Moneyline: +110)
• 4/16/2024: 3-1 SEA (Favorite: Mariners, Spread: -1.5, Total: 7, Favorite Moneyline: -142, Underdog Moneyline: +120)
• 4/15/2024: 9-3 SEA (Favorite: Mariners, Spread: -1.5, Total: 7, Favorite Moneyline: -154, Underdog Moneyline: +130)
• 9/6/2023: 8-4 SEA (Favorite: Mariners, Spread: -1.5, Total: 9.5, Favorite Moneyline: -174, Underdog Moneyline: +146)
• 9/5/2023: 7-6 CIN (Favorite: Mariners, Spread: -1.5, Total: 10.5, Favorite Moneyline: -152, Underdog Moneyline: +128)
• 9/4/2023: 6-3 CIN (Favorite: Mariners, Spread: -1.5, Total: 10.5, Favorite Moneyline: -158, Underdog Moneyline: +134)

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