Boston Red Sox vs Seattle Mariners Prediction – 6/18/2025

The Seattle Mariners and the Boston Red Sox meet for the third game of their series on June 18, 2025, at T-Mobile Park. Both teams are hovering around .500, with the Mariners sitting at 37-35 and the Red Sox at 38-37. This matchup has significant implications for both teams as they seek to gain momentum in a tightly contested American League landscape.

The Mariners will look for a second win in a row over the Red Sox behind Luis Castillo, who is projected to start. Castillo has had a decent season with a 4-4 record and a solid 3.29 ERA, ranking him as the 86th best starting pitcher in MLB. However, his 4.24 xFIP suggests he may have been a bit fortunate, raising concerns about his consistency.

On the other side, Garrett Crochet is slated to take the mound for the Red Sox. With a 6-4 record and an impressive 2.24 ERA, Crochet ranks 6th among starting pitchers, making him an elite option. His ability to rack up strikeouts (30.6 K%) will be crucial against a Mariners offense that ranks 5th in MLB for strikeouts this season.

Offensively, the Mariners rank 11th overall but struggle with a .235 batting average, placing them 19th. In contrast, the Red Sox boast a 6th-ranked offense, highlighted by a strong batting average of .262. Betting markets indicate a close matchup, with the Mariners holding a moneyline of +105 and the Red Sox at -125, reflecting a competitive atmosphere.

Quick Takes Boston Red Sox:

Garrett Crochet has gone to his four-seam fastball 10.7% less often this season (43%) than he did last year (53.7%).

• Fastballs are the one easiest pitches to hit and generate few strikeouts, so a pitcher who begins to use his fastball lessoften will likely be more effective than he used to be.

The Seattle Mariners have just 1 same-handed RP in their bullpen, so David Hamilton stands a good chance of holding the advantage against every reliever all game.

• Hitters perform worse against pitchers of the same handedness (i.e. righty-vs-righty), and being able to avoid those matchups against the bullpen boosts performance and creates hidden edge.

The underlying talent of the Boston Red Sox projected batting order today (.307 projected wOBA per the leading projection system, THE BAT X) figures to be quite a bit weaker than their .324 wOBA this year.

• Betting lines are often based on seasonal team quality. If today's lineup is watered down, however, there may be value if markets aren't accounting for the lower quality of this offense.

Quick Takes Seattle Mariners:

Luis Castillo's 94.4-mph velocity on his fastball this year is a big 1.1-mph decline from last year's 95.5-mph mark.

• Velocity is a key component to fastball success in generating strikeouts and preventing runs, so a pitcher whose velocity decreases will likely see worse results.

Bats such as Jorge Polanco with extreme flyball tendencies are usually more effective when facing pitchers like Garrett Crochet who skew towards the groundball end of the spectrum.

• This mostly has to do with the way the hitter's swing plane interacts with the pitch trajectory, and it can create boosted performance across all categories and hidden value few are considering.

Seattle Mariners hitters as a group grade out 8th- in baseball for power this year when assessing with their 9.4% Barrel%.

• Barrel% measures how often a player hits the ball at the optimal exit velocity and launch angle and is a terrific measure of underlying power.

Game Trends

• The Seattle Mariners have hit the Game Total Over in 33 of their last 59 games (+6.65 Units / 10% ROI)
• The Boston Red Sox have hit the 1st Five Innings (F5) Run Line in 17 of their last 24 away games (+11.90 Units / 44% ROI)
• Abraham Toro has hit the Total Bases Over in 14 of his last 20 games (+8.20 Units / 28% ROI)

Boston Red Sox vs Seattle Mariners Prediction

Predicted Final Score: Boston Red Sox 3.91, Seattle Mariners 3.57

• Date: June 18, 2025
• Venue: T-Mobile Park
• Starting Pitchers:
  • Garrett Crochet - Red Sox
  • Luis Castillo - Mariners

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