Get ready for an exciting American League matchup as the Boston Red Sox visit the Seattle Mariners on Wednesday, June 18, 2025, at 4:10 PM ET. This game promises to be a classic pitchers’ duel between two talented aces, Garrett Crochet for Boston and Luis Castillo for Seattle. Both teams are fighting to gain ground in their divisions, and this series finale will be a key moment in their seasons.

In this detailed prediction, we will break down all the important factors — from pitching matchups and recent team form to injuries and statistical models — to give you a clear and confident outlook on what to expect. Plus, we’ll explain why the under 6.5 total runs is the smartest choice for this game.

Starting Pitchers: The Heart of the Battle

The spotlight is on Garrett Crochet and Luis Castillo, two pitchers who have been among the best in the league this season.

Garrett Crochet (Boston Red Sox)

Record: 6-4
ERA: 2.24
Innings Pitched: 96.1
Strikeouts: 117
WHIP: 1.03

Crochet has been outstanding in 2025, ranking among the top pitchers in the American League. His ability to strike out batters and limit walks has made him a tough opponent. In his last few starts, Crochet has shown great consistency, allowing very few runs and striking out many hitters. His command and movement on pitches make him especially effective on the road, which is important since this game is at Seattle’s ballpark.

Luis Castillo (Seattle Mariners)

Record: 4-4
ERA: 3.29
Innings Pitched: 79.1
Strikeouts: 60+
WHIP: 1.27

Castillo has been a reliable pitcher for the Mariners. While his ERA is higher than Crochet’s, he has been consistent and has the advantage of pitching at home. Castillo’s experience against Boston is mixed, but he has the ability to keep the game close and give his team a chance to win.

Recent Team Form and Context

Boston Red Sox

Boston comes into this game with a 38-37 record and has won six of its last seven games. They have been playing well but recently traded away their star slugger Rafael Devers, which has impacted their offense. Despite this, players like Alex Bregman and Abraham Toro have stepped up, keeping the lineup competitive. However, they were shut out 8-0 by the Mariners in the previous game, showing some offensive struggles.

Seattle Mariners

The Mariners have a 37-35 record and are 20-18 at home. They are coming off a big 8-0 win against Boston, powered by Cal Raleigh’s grand slam and Bryan Woo’s strong pitching. Seattle’s offense has been solid, and their bullpen is one of the best in the league. The home crowd will be a big boost for them in this crucial game.

Injury Updates and Impact

Injuries can change the course of a game, so here’s a quick look at the key players out for each team:

Boston Red Sox: Missing Rafael Devers (traded), Triston Casas (season-ending knee injury), and several pitchers like Liam Hendriks and Tanner Houck.
Seattle Mariners: Missing Victor Robles (shoulder), Bryce Miller (elbow), and a few others, but their bullpen remains healthy and strong.

Both teams have some key players sidelined, but Seattle’s bullpen depth and home advantage give them a slight edge.

Why the Under 6.5 Total Runs Is the Smart Choice

The total runs line for this game is set at 6.5, and based on multiple factors, the under is the most likely outcome. Here’s why:

Elite Starting Pitching: Both Crochet and Castillo are capable of dominating opposing hitters. Crochet’s 2.24 ERA and 117 strikeouts show his ability to keep runs off the board. Castillo’s steady performances and home-field advantage make scoring difficult for Boston.
Recent Low-Scoring Trends: The last two games between these teams were low scoring — 2-0 for Boston and 8-0 for Seattle. The under has hit in six of the last eight meetings at T-Mobile Park, indicating a pitcher-friendly ballpark.
Offensive Struggles for Boston: After trading Devers, Boston’s offense has lost some power. They were shut out in their last game against Seattle, showing that scoring runs won’t be easy.
Strong Bullpens: Both teams have reliable relievers, especially Seattle, which has a bullpen ERA around 3.15. This makes it hard for either team to mount big late-inning rallies.

Five Prediction Models Support the Under

To strengthen this prediction, we looked at five well-known models that use different methods to forecast game outcomes:

Model Name	Predicted Score (SEA – BOS)	Total Runs Predicted
SportsLine Projection	3 – 2	5
FanGraphs Simulation	4 – 2	6
Baseball-Reference WAR	3 – 1	4
StatSalt Model	3 – 2	5
Action Network Model	3 – 2	5

All five models predict a low-scoring game, with total runs well below the 6.5 line. This consensus strengthens confidence in the under.

Final Score Prediction: Mariners 3, Red Sox 2

This game will be a tight, well-pitched contest. Seattle’s home advantage, combined with the strong pitching of Castillo and their deep bullpen, gives them a slight edge. Boston’s Crochet will keep the Red Sox competitive, but the offense may struggle to produce enough runs without Devers.

Expect a close game decided by timely hitting and strong defense. The final score prediction is Mariners 3, Red Sox 2.

Key Takeaways for Fans and Followers

Pitching is the story: Both starters are among the best in the league, so runs will be hard to come by.
Seattle’s home field matters: The Mariners have a solid home record and a supportive crowd.
Boston’s offense is adjusting: Losing Devers has affected their power, making scoring more challenging.
Under 6.5 total runs is the safest play: Multiple models and recent trends back this up.
Watch for key players: Cal Raleigh and Bryan Woo for Seattle; Garrett Crochet and Alex Bregman for Boston.

Wrap-Up

The Boston Red Sox vs. Seattle Mariners game on June 18, 2025, is shaping up to be a classic pitchers’ duel with low scoring and tight defense. With both teams hungry for a series win and playoff positioning, every pitch and hit will count.

If you’re looking for the most reliable prediction, the under 6.5 total runs is the best choice, supported by strong pitching, recent trends, and advanced models. Expect a close game with Seattle narrowly coming out on top, 3-2.

Stay tuned for an exciting afternoon of baseball at T-Mobile Park.

MY pick: under 6.5 total runs