Check Out the Mariners vs Rays Betting Guide and Expert Picks – 9/1/2025

Seattle Mariners

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Tampa Bay Rays

The matchup on September 1, 2025, features the Tampa Bay Rays hosting the Seattle Mariners at George M. Steinbrenner Field. This game is significant as it marks the first in a series between two teams with differing fortunes this season. The Rays, currently sitting at 67-69, have been having an average season, while the Mariners boast a stronger record of 73-64, indicating an above-average performance.

In their most recent outings, the Mariners have continued to show their power, with a robust lineup that ranks 3rd in MLB for home runs, totaling 195 this season. However, they face a challenge against Shane Baz, projected to start for the Rays. Baz, despite his 5.19 ERA, has an xFIP of 3.89, suggesting he has been somewhat unlucky and may perform better than his numbers indicate. His groundball rate of 48% could work in his favor against a powerful Mariners offense that thrives on home runs.

On the other side, Luis Castillo is set to take the mound for Seattle. Despite being rated as an average pitcher, he has a solid 3.75 ERA. However, projections indicate that he may be due for a regression based on his xERA of 4.37. Castillo’s low walk rate of 6.7% could be beneficial against a Rays offense that draws the 4th least walks in MLB.

The Rays’ offense ranks 16th overall but leads the league in stolen bases, which could create additional pressure on Castillo. With a game total set at 8.5 runs, and the betting markets favoring the Mariners slightly, this game is poised to be tightly contested, especially with both teams’ bullpens ranked in the top 10. The projections suggest the Rays may have a better chance than the odds reflect, making them an intriguing option for bettors looking for value.

Seattle Mariners Insights

• Luis Castillo – Over/Under 4.5 Strikeouts (-120/-110)
  Despite conventional wisdom, fastballs are generally a pitcher’s least effective pitch. Luis Castillo has gone to his secondary pitches 5.6% less often this season (31%) than he did last year (36.6%).
  Explain: Fastballs are the one easiest pitches to hit and generate few strikeouts, so a pitcher who begins to use his fastball more often will likely be less effective than he used to be.
• Jorge Polanco – Over/Under 0.5 Hits (-170/+135)
  Jorge Polanco is projected to bat 6th on the lineup card in this matchup, which would be a downgrade from his 68% rate of hitting in the top-half of the lineup this year.
  Explain: The lower in the order a player bats, the fewer plate appearances he will get and the fewer opportunities he will get to hit the Over for every market. A player who hits lower in the order than he normally does may provide extra value opportunity since the market may be based on him hitting higher.
• Seattle Mariners – 2H Moneyline
  The Seattle Mariners bullpen ranks as the 9th-best in Major League Baseball, according to the leading projection system (THE BAT).
  Explain: Most bettors only consider the starting pitcher, but a strong bullpen sneakily creates a tougher matchup for the opposing offense and suppresses a game’s runs.

Tampa Bay Rays Insights

• Shane Baz – Over/Under 5.5 Strikeouts (-150/+115)
  Among all starters, Shane Baz’s fastball velocity of 96.2 mph grades out in the 91st percentile this year.
  Explain: Velocity is a key component to fastball success in generating strikeouts and preventing runs.
• Junior Caminero – Over/Under 1.5 Total Bases (+100/-130)
  Junior Caminero has been hot of late, raising his seasonal exit velocity of 92.1-mph to 97-mph over the past 7 days.
  Explain: Hitting the ball hard increases the chances of either a home run or the ball landing in fair territory for a hit before a fielder can get to it.
• Yandy Diaz – Over/Under 1.5 Total Bases (+120/-155)
  Yandy Diaz has a 100th percentile opposite-field rate on his flyballs (43%) and will have a big advantage hitting them in the direction of the league’s 5th-shallowest RF fences in today’s game.
  Explain: This player’s skill set matches up particularly well with the park he’s in today, which may lead to better-than-usual performance.

Betting Trends

• Tampa Bay Rays – Over/Under 3.5 Team Total (-145/+115)
  The Tampa Bay Rays have hit the Team Total Under in 74 of their last 127 games (+13.85 Units / 9% ROI)
• Over/Under 8.5 Game Total (-110/-110)
  The Seattle Mariners have hit the Game Total Over in 67 of their last 123 games (+9.90 Units / 7% ROI)
• Chandler Simpson – Over/Under 0.5 Singles (-220/+165)
  Chandler Simpson has hit the Singles Over in 17 of his last 20 games at home (+12.60 Units / 38% ROI)