Mariners vs Red Sox Prediction, Odds, Moneyline, Spread & Over/Under for June 21

Odds updated as of 12:12 a.m.

The Seattle Mariners are among the MLB teams busy on Sunday, up against the Boston Red Sox.

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

Mariners vs Red Sox Game Info

• Seattle Mariners (39-38) vs. Boston Red Sox (30-43)
• Date: Sunday, June 21, 2026
• Time: 4:10 p.m. ET
• Venue: T-Mobile Park -- Seattle, Washington
• Coverage: Mariners.TV and NESN

Mariners vs Red Sox Odds & Moneyline

• All MLB odds, betting lines and prop bets are available on FanDuel Sportsbook.
• Moneyline: SEA: (-144) | BOS: (+122)
• Spread: SEA: -1.5 (+162) | BOS: +1.5 (-196)
• Total: 7 -- Over: (-102) | Under: (-120)

Mariners vs Red Sox Probable Starting Pitchers

Probable Pitchers: Logan Gilbert (Mariners) - 5-4, 3.43 ERA vs Payton Tolle (Red Sox) - 3-4, 2.93 ERA

The probable starters are Logan Gilbert (5-4) for the Mariners and Payton Tolle (3-4) for the Red Sox. Gilbert's team is 6-9-0 against the spread this season in his starts. Gilbert's team is 9-4 this season when he starts and they are the moneyline favorite. The Red Sox have a 2-8-0 record against the spread in Tolle's starts. The Red Sox are 1-4 in Tolle's five starts this season that they were the moneyline underdog.

Mariners vs Red Sox Prediction & Pick

All MLB win probability predictions and picks are according to numberFire.
Prediction: Mariners win (58.3%)

Mariners vs Red Sox Moneyline

• Looking at the moneyline for Mariners-Red Sox, Seattle is the favorite at -144, and Boston is +122 playing on the road.

Mariners vs Red Sox Spread

• The Red Sox are +1.5 on the run line against the Mariners. The Red Sox are -196 to cover, and the Mariners are +162.

Mariners vs Red Sox Over/Under

• Mariners versus Red Sox, on June 21, has an over/under of 7, with the over being -102 and the under -120.

Bet on Seattle Mariners vs. Boston Red Sox on FanDuel today!

Mariners vs Red Sox Betting Trends

• The Mariners have been favorites in 69 games this season and have come away with the win 36 times (52.2%) in those contests.
• This season Seattle has been victorious 16 times in 25 chances when named as a favorite of at least -144 on the moneyline.
• The Mariners' games have gone over the total in 37 of their 76 opportunities.
• The Mariners are 28-48-0 against the spread in their 76 games with a line set by sportsbooks this season.
• The Red Sox have won 10 of the 26 games they were listed as the moneyline underdog this season (38.5%).
• In games it has played as a moneyline underdog with odds of +122 or longer, Boston has a record of 1-6 (14.3%).
• The Red Sox have played in 73 games with a set over/under, and have combined with opponents to go over the total 33 times (33-38-2).
• The Red Sox have a 30-43-0 record ATS this season (covering 41.1% of the time).

Mariners Player Leaders

• Julio Rodriguez has an OPS of .745, fueled by an OBP of .309 and a team-best slugging percentage of .436 this season. He has a .249 batting average.
• Among all qualifying hitters in the majors, his batting average ranks 86th, his on-base percentage ranks 117th, and he is 72nd in slugging.
• Rodriguez will look for his fourth straight game with a hit in this contest. During his last five outings he is hitting .158 with a double, a home run, a walk and three RBIs.
• Josh Naylor is hitting .253 with nine doubles, eight home runs and 23 walks. He's slugging .372 with an on-base percentage of .314.
• He ranks 76th in batting average, 106th in on-base percentage and 119th in slugging among qualified hitters.
• Naylor enters this game looking to extend his three-game hit streak. During his last five outings he is batting .200 with two doubles, a home run and an RBI.
• Cole Young has collected 71 base hits, an OBP of .317 and a slugging percentage of .366 this season.
• Dominic Canzone has been key for Seattle with 49 hits, an OBP of .355 plus a slugging percentage of .552.

Red Sox Player Leaders

• Willson Contreras has totaled 73 hits with a .382 on-base percentage, leading the Red Sox in both statistics. He's batting .289 and slugging .538.
• He is 18th in batting average, 14th in on-base percentage and 11th in slugging percentage among all qualifying hitters in the majors.
• Wilyer Abreu's .423 slugging percentage paces his team. He has a batting average of .274 with an on-base percentage of .332.
• He is currently 47th in batting average, 84th in on-base percentage and 80th in slugging percentage among all qualifying hitters.
• Ceddanne Rafaela is hitting .286 with 17 doubles, two triples, seven home runs and 14 walks.
• Jarren Duran is hitting .210 with nine doubles, two triples, 12 home runs and 20 walks.

Mariners vs Red Sox Head to Head

• 6/19/2026: 6-2 BOS (Favorite: Mariners, Spread: -1.5, Total: 6.5, Favorite Moneyline: -112, Underdog Moneyline: -104)
• 6/18/2025: 3-1 BOS (Favorite: Red Sox, Spread: -1.5, Total: 6.5, Favorite Moneyline: -118, Underdog Moneyline: -100)
• 6/17/2025: 8-0 SEA (Favorite: Mariners, Spread: -1.5, Total: 7, Favorite Moneyline: -162, Underdog Moneyline: +136)
• 6/16/2025: 2-0 BOS (Favorite: Mariners, Spread: -1.5, Total: 7, Favorite Moneyline: -178, Underdog Moneyline: +150)
• 4/24/2025: 4-3 SEA (Favorite: Red Sox, Spread: -1.5, Total: 8, Favorite Moneyline: -180, Underdog Moneyline: +152)
• 4/23/2025: 8-5 SEA (Favorite: Red Sox, Spread: -1.5, Total: 9.5, Favorite Moneyline: -136, Underdog Moneyline: +116)
• 4/22/2025: 8-3 BOS (Favorite: Red Sox, Spread: -1.5, Total: 9.5, Favorite Moneyline: -122, Underdog Moneyline: +104)
• 7/31/2024: 3-2 BOS (Favorite: Mariners, Spread: -1.5, Total: 9.5, Favorite Moneyline: -112, Underdog Moneyline: -104)
• 7/30/2024: 10-6 SEA (Favorite: Mariners, Spread: -1.5, Total: 10.5, Favorite Moneyline: -118, Underdog Moneyline: -100)
• 7/29/2024: 14-7 BOS (Favorite: Red Sox, Spread: -1.5, Total: 8.5, Favorite Moneyline: -120, Underdog Moneyline: +102)

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