The Boston Red Sox visit the Seattle Mariners on Saturday night at T-Mobile Park, and the market sees a close game. Seattle sits at -128 on the moneyline, while Boston comes back at +107. The total is set at a modest 7.5 runs. Pitching headlines this one. Rookie left-hander Connelly Early takes the ball for Boston against Seattle right-hander Emerson Hancock. Our lean tilts to the home side, yet the rookie's strikeout upside keeps the Red Sox live as a short underdog. Below, we break down the matchup, the line, and our picks.
Last Updated: Saturday, June 20, 2026
BOSTON RED SOX VS SEATTLE MARINERS JUNE 20, FIRST PITCH & HOW TO WATCH | |
|---|---|
| Where | T-Mobile Park, Seattle WA |
| When | Saturday, June 20 – 10:10 PM ET |
| TV | NESN, Seattle Mariners Network, MLB.TV |
Boston Red Sox vs. Seattle Mariners Game Preview
The pitching matchup sets the tone. Hancock has been a steady piece for Seattle, sitting at 5-3 with a 3.28 ERA across 79.2 innings. He misses bats at a fair clip, with an 8.5 K/9 and a .220 average against. His last outing told a different story, however. Washington tagged him for six runs over four innings on June 14, and his command of the sweeper wobbled. The Mariners are also running a piggyback pitching plan, so a second arm is likely to follow Hancock for bulk innings.
Boston counters with rookie left-hander Connelly Early. The 24-year-old carries a 5-5 record and a 3.81 ERA, and his swing-and-miss stuff has drawn attention since his 2025 debut. Early gives the Red Sox a live arm, but rookies can be volatile on the road. Seattle's lineup is steady at home, where the Mariners are 21-17 this season.
The records frame the bigger picture. Seattle enters at 39-37 and sits atop the AL West. Boston enters at 29-43 and last in the AL East, 15.5 games back. The Red Sox have lost four straight and dropped eight of their last 10, including a sweep at the hands of Toronto. Still, Boston travels better than it plays at home, with a 17-18 road mark. Meanwhile, Seattle has been ordinary lately at 5-5 over its last 10. So the gap on paper is wider than recent form alone suggests.
BOSTON RED SOX VS SEATTLE MARINERS ODDS | |||
|---|---|---|---|
| Run Line | Moneyline | Total | |
| BOSTON RED SOX | +1.5 (-200) | +107 | U 7.5 (-120) |
| SEATTLE MARINERS | -1.5 (+170) | -128 | O 7.5 (+100) |
Odds accurate as of June 20, 2026 via TheSpread.com. Odds change, get the latest MLB Odds - Futures - Props
BOSTON RED SOX VS SEATTLE MARINERS WHO IS THE PUBLIC BETTING? | |||
|---|---|---|---|
| BOSTON RED SOX | 25% | 75% | SEATTLE MARINERS |
See the latest MLB Public Betting Splits and make smarter wagers!
Moneyline Pick — Seattle Mariners ML
The Pick: Seattle Mariners Moneyline (-128)
This is a short price for a reason. Seattle owns the better record, the deeper staff, and home-field comfort. The run line is the trap here. Asking Seattle to win by two or more at -1.5 (+170) is a stretch in a game with a 7.5-run total, so the moneyline is the cleaner route. The Mariners also draw a Red Sox club that is reeling, having lost four in a row and eight of 10. Backing the home favorite at a modest -128 fits the profile.
The case against is real, though. Hancock just gave up six runs in his last start, and the piggyback plan adds a layer of uncertainty about who pitches the middle innings. Early brings strikeout upside that can quiet a lineup for a few turns. The public is also heavy on Seattle at 75%, which trims any value on the favorite. Boston's better road form is another caution flag. The Red Sox at +107 are a defensible underdog play for bettors who want to fade a one-sided market.
Total Pick — Under 7.5
The Pick: Under 7.5 (-120)
Several factors point under. T-Mobile Park has long played as a pitcher-friendly venue, and a 7.5-run total already reflects that. Boston's bats are cold, and the Red Sox have averaged under four runs per game this season. Hancock misses bats when his sweeper is on, and Early carries strong strikeout rates of his own. Two arms with swing-and-miss profiles in a run-suppressing park is a recipe for a lower-scoring night.
The other side has merit. Hancock's command slipped in his last start, and the piggyback relievers behind him are not certain to hold a lead cleanly. If Boston's young hitters square up the fastball early, the under tightens quickly. Still, the park, the price, and Boston's offensive slump tilt the lean to the under here.
Final Thoughts and Bonus Angle
The bonus angle lives in the first five innings. With Seattle leaning on a piggyback plan and Boston sending a strikeout-heavy rookie, the early frames could stay quiet before either bullpen takes over. A first-five-innings under is worth a look for bettors who want to sidestep late-inning relief risk. The case against it is simple. If Hancock's command falters again, the runs can come early rather than late.
One thing to watch is Seattle's late-inning bullpen. The Mariners have had bumpy outings from their back-end arms this season, so a one-run lead is not safe until the final out. That risk is part of why the run line is so pricey. For now, our card is built around the better team at a fair price and a total that respects the park.
Picks summary: Seattle Mariners Moneyline (-128), Under 7.5 (-120), and a lean to the first-five-innings under as a bonus angle. For more plays across the slate, see our latest MLB best bets, and for more on Boston's recent skid, read our Blue Jays vs. Red Sox preview.
MLB Mariners Prediction FAQ
What time does the Boston Red Sox vs. Seattle Mariners game start?
First pitch is scheduled for 10:10 PM ET on Saturday, June 20, 2026, at T-Mobile Park in Seattle.
What channel is the Boston Red Sox vs. Seattle Mariners game on?
The game is carried on NESN in the Boston market, the Seattle Mariners regional broadcast, and MLB.TV.
Who is pitching for the Mariners on Saturday?
Right-hander Emerson Hancock is the projected starter for Seattle. He carries a 5-3 record and a 3.28 ERA on the season.
Who is favored in the Boston Red Sox vs. Seattle Mariners game?
The Seattle Mariners are the home favorite at -128 on the moneyline. The Boston Red Sox are the underdog at +107.