The Boston Red Sox host the Seattle Mariners on April 22, 2025. First pitch from Fenway Park is scheduled for 6:45 p.m. EDT; the game will be broadcast on NESN.
The Red Sox will welcome a key arm back to the rotation when they open up a three-game series Tuesday versus the Mariners. Last year's Opening Day starter, Brayan Bello, is set to make his first start of the season versus Bryce Miller. Bello had a relatively disappointing 2024 campaign, pitching to an ERA of 4.49 over 162 1/3 innings, but could be poised for a breakout this season.
Find my MLB betting preview and Mariners vs Red Sox prediction for Tuesday below.
My Mariners vs Red Sox Prediction
- Mariners vs Red Sox pick: Boston Red Sox First 5 Moneyline -125 (Play to -130)
My Mariners vs Red Sox best bet is Boston Red Sox F5 Moneyline. Make sure to find the best odds by checking our live MLB odds page.
Mariners vs Red Sox Odds
| Mariners Odds | ||
|---|---|---|
| Spread | Total | Moneyline |
+1.5 -200 | 9 -105o / -115u | +110 |
| Red Sox Odds | ||
|---|---|---|
| Spread | Total | Moneyline |
-1.5 +165 | 9 -105o / -115u | -130 |
Mariners vs Red Sox Projected Starting Pitchers
| RHP Bryce Miller (SEA) | Stat | RHP Brayan Bello (BOS) |
|---|---|---|
| 1-2 | W-L | 0-0 (Season Debut) |
| 0.5 | fWAR (FanGraphs) | — |
| 3.43/3.33 | ERA /xERA | — |
| 3.09/4.26 | FIP / xFIP | — |
| 1.33 | WHIP | — |
| 12.8 | K-BB% | — |
| 31.5 | GB% | — |
| 103 | Stuff+ | — |
| 89 | Location+ | — |
Nick Martin’s Mariners vs Red Sox Preview
Seattle Mariners Betting Preview: Can Power Surge Continue?
The Mariners enter this series in strong form as they hold an 8-2 record over their past 10 games and had a highly productive series over the weekend versus a solid Toronto Blue Jays pitching staff. They currently hold a sixth ranked wRC+ of 115, after finishing with a 104 wRC+ in 2024 with the league's worst strikeout rate.
Led by Cal Raleigh, who's already hit nine home runs, the Mariners rank fifth in baseball with 32 home runs throughout their first 22 games.
The Mariners offense could be a likely candidate for regression, though, as the depth of the lineup behind Julio Rodriguez, Randy Arozarena and Raleigh still looks to be a concern, and if that trio comes down to earth with regard to power, a lack of production from further down the lineup will look to be a more noteworthy flaw.
The general consensus from the major projection systems was that the Mariners would be near the lower third of the MLB in terms of offensive production, and to this point they are greatly overachieving preseason expectations offensively.
Miller had an excellent breakout campaign in 2024, pitching to an ERA of 2.94 across 180 1/3 innings. While he's gotten off to a strong start in 2025 with a 3.43 ERA and 3.33 xERA across 21 innings, there are some arguments that suggest he could be due for regression in the near future.
Miller's K-BB% is down to 12.8% compared to last year's mark of 17.9%, and his xFIP is up considerably to 4.26. He holds a Pitching+ rating of 92, which is down considerably compared to last season.
Miller was drastically more effective last season when pitching at the very pitcher-friendly confines of T-Mobile Park in Seattle. He held a 1.96 ERA at home compared to a 4.07 ERA on the road. It appears likely that trend will continue in 2025, as he's allowed a .404 slug rate and .277 batting average on the road.
Boston Red Sox Betting Preview: All Eyes on Bello
Bello will make his season debut after four rehab starts, and all reports regarding those outings stated that Bello's stuff looked quite good despite modest results. Bello's four-seamer touched 98 mph in his last rehab start, and his slider reportedly looked quite sharp.
As is evidenced by the Netflix series The Clubhouse: A Year with the Red Sox, Bello dealt with a tough situation off of the field last year, as his wife could not get a visa, and therefore his family remained in the Dominican Republic.
With that situation resolved, Bello may be in a better place mentally this season and could be poised to build on what was a strong second half last year. Bello held a 3.47 ERA across 72 and 2/3 innings of work in the second half of the 2024 season.
Bello has the stuff to be a high-quality starter, but has had command issues early on in his career. However, Bello walked only four batters across 12 innings during his rehab outings and could have a significant breakout this season if he can continue to control his quality four-pitch mix.
The Red Sox hold a wRC+ rating of 104 versus right-handed pitching this season and rank fourth in hard-hit rate. Several of the Red Sox top batters, such as Rafael Devers, Jarren Duran, Triston Casas and Wilyer Abreu, project to be very hard on righties this season, and their lineup will provide a tough test for Miller.
Mariners vs Red Sox Prediction, Betting Analysis
This being Bello's first start of the season adds a layer of volatility to this matchup, but there are a number of arguments that suggest this game is a good spot to back him right out of the gates. The Mariners offensive upside still looks to be quite middling, and they provide a good opponent to back a potentially undervalued starter in Bello.
Miller has gotten off to a strong start where it counts, but his underlying profile is not overly convincing, and he will be trying to keep what should be one of baseball's better lineups versus RHP in check. He's been far less effective away from pitcher friendly T-Mobile Park throughout his career, and this matchup seems like a good time to buy into that trend.
At -125 I see value in backing the Red Sox to win the first five innings in Tuesday's series opener.
Pick: Boston Red Sox First 5 Moneyline -125 (Play to -130)
Moneyline
There looks to be some value in backing the Red Sox at -130 to win this game, but given the strength of the Mariners' bullpen, I personally see more value in taking a better price (-125) to isolate the Miller vs. Bello innings.
Run Line (Spread)
Backing the Red Sox to cover the spread at +160 provides some value and would hold a similar EV to betting on them to win the game.
Over/Under
A total of 9 looks fair to me in this matchup. Bello has the potential to be much improved this season, but we haven't seen it yet, and part of the reason I'm high on the Red Sox in this game is my belief that Miller appears poised for regression.
Mariners vs Red Sox Parlay
- Boston Red Sox -1.5
- Bello Over 4.5 Strikeouts
- Devers Over 1.5 Total Bases
Parlay odds: +600 (BetMGM)
As outlined, Miller could be due to come down to earth in the near future, and I believe the potential is there for the Red Sox to hit him quite effectively in this matchup. If the Red Sox can do some damage off of Miller early on, they should avoid having to face the Mariners elite high-leverage relievers, and this looks like a decent spot to target the Sox winning by several runs.
Bello has the stuff to rack up Ks at a higher rate than we saw in 2024, which was evident in his final relief start when he struck out four of the last seven batters he faced. The Mariners continue to strike out at a higher than league average rate and have plenty of good targets further down the lineup.
Devers nightmare start to the season seems to be in the distant past now, and his underlying metrics are tremendous. He holds a hard-hit rate of 62.7% this season, and is in the 96th percentile in terms of barrel rate. Despite his awful start to the year, he has still slugged .426 versus righties in 2025, after slugging .601 versus righties in 2024.
