Boston Red Sox vs Seattle Mariners Picks and Prediction for Sunday, June 21, 2026
Use Code WWWC The Boston Red Sox visit the Seattle Mariners at T-Mobile Park on Sunday at 4:10 PM ET on MLB.TV. Boston enters at 30-43 and sits last in the AL East, while Seattle is 39-38 and leads the AL West. The Red Sox snapped a four-game losing streak with a 6-2 win in Friday's series opener and improved to 18-18 on the road. Seattle had won two of its previous three games before that loss and continues to stay in contention thanks to one of the better pitching staffs in baseball. Sunday's finale features rookie left-hander Payton Tolle facing veteran right-hander Logan Gilbert. Cash in a winning ticket with our free MLB picks.
Red Sox Trying to Build Momentum After Friday's Win
Boston has struggled for consistency throughout the season, but Friday's victory was a much-needed boost after a rough stretch. The Red Sox have dropped four of their last five games overall and remain 15.5 games behind the Yankees in the AL East. Despite the record, Boston continues to get solid work from its pitching staff, entering Sunday with a 3.90 ERA and 1.27 WHIP.
The offense has been more uneven. Boston is batting .245 with 288 runs scored and 62 home runs through 73 games. Willson Contreras has been the clear leader, hitting .289 with 16 home runs, 44 RBI, and a .919 OPS. Wilyer Abreu is batting .274 with 77 hits, while Ceddanne Rafaela owns a .286 average and 32 RBI. Jarren Duran has added 12 home runs and 37 RBI despite a lower batting average.
Boston will hand the ball to Payton Tolle, a left-hander who has been one of the bright spots on the roster. Tolle is 3-4 with a 2.93 ERA and 1.06 WHIP across 58.1 innings. He has allowed only 46 hits while striking out 60 batters. The rookie has pitched well away from home, posting a 3.16 ERA in four road starts. If Boston wants to secure another road series win, Tolle will need to continue his strong form.
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Injuries: Isiah Kiner-Falefa, Noah Song, Jovani Moran, Triston Casas, Johan Oviedo.
Mariners Counting on Gilbert and Strong Home Pitching
Seattle enters Sunday with a 39-38 record and has relied heavily on its pitching staff throughout the season. The Mariners own a 3.64 ERA and 1.18 WHIP, both among the best marks in Major League Baseball. Seattle pitchers have also recorded 668 strikeouts while holding opponents to a .240 batting average.
The Mariners' offense has produced 322 runs and 97 home runs despite a .234 team batting average. Julio Rodriguez leads the lineup with 14 home runs and 37 RBI. Randy Arozarena is batting .291 with a .377 OBP, while Luke Raley has clubbed 14 home runs. Dominic Canzone has also provided quality production, hitting .282 with 11 homers and a .907 OPS.
Seattle turns to Logan Gilbert, a right-hander who continues to be one of the most dependable starters in the American League. Gilbert is 5-4 with a 3.43 ERA and 1.03 WHIP across 86.2 innings. He has struck out 92 batters and issued only 20 walks. Gilbert enters this matchup after allowing just two earned runs over his last 18.1 innings while recording 23 strikeouts.
Injuries: Luke Raley, Randy Arozarena, Will Wilson, Brendan Donovan, Dane Dunning.
Pitching Matchup
Boston Red Sox – Payton Tolle (Left-Hander)
Tolle is 3-4 with a 2.93 ERA and 1.06 WHIP. The left-hander has allowed only five home runs in 58.1 innings while striking out 60 batters.
Seattle Mariners – Logan Gilbert (Right-Hander)
Gilbert is 5-4 with a 3.43 ERA and 1.03 WHIP across 86.2 innings. The right-hander has recorded 92 strikeouts and is in excellent recent form.
Boston Red Sox vs Seattle Mariners Pick
- Seattle Mariners ML
Gilbert gives Seattle a slight edge in what projects as a low-scoring game. The Mariners own the better overall pitching staff, have been strong at home, and continue to limit opposing offenses better than Boston. With Gilbert pitching well and Seattle fighting for first place in the AL West, the Mariners are positioned to bounce back after Friday's loss.
Boston Red Sox vs Seattle Mariners Over/Under Pick
- Under
Both starting pitchers have been reliable this season. Tolle owns a 2.93 ERA and has been effective on the road, while Gilbert enters after three straight strong outings. Seattle ranks among the league leaders in ERA, and Boston's offense has struggled for stretches throughout the season. Expect a tight game with limited scoring opportunities and strong pitching on both sides.
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