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

Odds updated as of 3:12 p.m.

On Sunday in MLB, the Seattle Mariners are up against the Boston Red Sox.

All the information you need to make smart bets on this game at FanDuel Sportsbook can be found below. Check out all of the latest MLB betting lines here.

Mariners vs Red Sox Game Info

• Seattle Mariners (39-39) vs. Boston Red Sox (31-43)
• 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: (-122) | BOS: (+104)
• Spread: SEA: -1.5 (+180) | BOS: +1.5 (-220)
• Total: 7.5 -- Over: (+100) | Under: (-122)

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 Mariners will give the nod to Logan Gilbert (5-4, 3.43 ERA), who is eyeing win No. 6 on the season, and the Red Sox will counter with Payton Tolle (3-4, 2.93 ERA). Gilbert and his team have a record of 6-9-0 against the spread when he starts. Gilbert's team has won 69.2% of his starts when they are favored on the moneyline (9-4). The Red Sox have a 2-8-0 record against the spread in Tolle's starts. The Red Sox have been the moneyline underdog in five of Tolle's starts this season, and they went 1-4 in those games.

Mariners vs Red Sox Prediction & Pick

All MLB win probability predictions and picks are according to numberFire.
Prediction: Mariners win (58%)

Mariners vs Red Sox Moneyline

• The Mariners vs Red Sox moneyline has Seattle as a -122 favorite, while Boston is a +104 underdog on the road.

Mariners vs Red Sox Spread

• The Mariners are 1.5-run home favorites on the runline against the Red Sox. The Mariners are +180 to cover, and the Red Sox are -220.

Mariners vs Red Sox Over/Under

• The Mariners-Red Sox contest on June 21 has been given an over/under of 7.5 runs. The over is set at +100 and the under at -122.

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Mariners vs Red Sox Betting Trends

• The Mariners have come away with 36 wins in the 70 contests they have been listed as the favorites in this season.
• This season Seattle has come away with a win 32 times in 59 chances when named as a favorite of at least -122 on the moneyline.
• The Mariners and their opponents have gone over the total this season in 37 of their 77 opportunities.
• The Mariners are 28-49-0 against the spread in their 77 games with a line set by sportsbooks this season.
• The Red Sox are 11-16 in games they were listed as the moneyline underdog (winning 40.7% of those games).
• Boston is 6-14 (winning only 30% of its games) when playing as a moneyline underdog of +104 or longer.
• In the 74 games oddsmakers have set an over/under for the Red Sox, they have combined with opponents to go over the total 33 times (33-39-2).
• The Red Sox are 31-43-0 against the spread this season.

Mariners Player Leaders

• Julio Rodriguez has an OPS of .740, fueled by an OBP of .309 and a team-best slugging percentage of .432 this season. He has a .247 batting average.
• Among all qualified hitters in baseball, his batting average ranks 90th, his on-base percentage ranks 116th, and he is 75th in slugging.
• Josh Naylor is hitting .253 with nine doubles, eight home runs and 23 walks, while slugging .370 with an on-base percentage of .313.
• He is 76th in batting average, 105th in on-base percentage and 121st in slugging among qualifying hitters.
• Naylor has picked up a hit in four games in a row. During his last five outings he is hitting .211 with two doubles and an RBI.
• Cole Young is batting .252 with a .362 slugging percentage and 34 RBI this year.
• Dominic Canzone has 11 home runs, 31 RBI and a batting average of .280 this season.

Red Sox Player Leaders

• Willson Contreras has put up an on-base percentage of .383 and has 73 hits, both team-high figures for the Red Sox. He's batting .286 and slugging .533.
• Including all the qualified players in MLB, his batting average is 22nd, his on-base percentage is 13th, and he is 14th in slugging.
• Wilyer Abreu is slugging .433 to lead his team. He has a batting average of .275 with an on-base percentage of .334.
• His batting average is 43rd among all qualified players, his on-base percentage ranks 81st, and he is 73rd in slugging.
• Ceddanne Rafaela has 17 doubles, two triples, seven home runs and 14 walks while batting .286.
• Jarren Duran is batting .207 with nine doubles, two triples, 12 home runs and 20 walks.

Mariners vs Red Sox Head to Head

• 6/20/2026: 5-1 BOS (Favorite: Mariners, Spread: -1.5, Total: 7.5, Favorite Moneyline: -122, Underdog Moneyline: +104)
• 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)

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