MLB Over/Under Best Bet: Athletics vs. Seattle Mariners, March 28

Nice start to the year yesterday with that under victory in Miami. Opting for the first-five-inning route rather than the full duration proved to be the difference, given that the full-game total moved past the number of 6.5.

We now travel to the Pacific Northwest on the opposite side of the country, where the Seattle Mariners are hosting the Athletics in the second contest of their season-opening four-game set.

It is interesting that Seattle elected to keep largely the same roster as the 2024 version, one that missed the playoffs by exactly one game for the second year in a row. Keeping the pitching staff together was smart after the Mariners registered the lowest starters' ERA of all 30 teams (3.38).

Sticking with the same batting order, though? That’s certainly a choice and could point to a repeat of a standout tendency that arguably held back the M’s in the prior campaign from achieving much more.

This club struggled when facing a left-handed pitcher. In fact, the Mariners had the lowest team batting average against lefties in all of baseball with a .213 mark – even worse than the historically bad Chicago White Sox (.220).

The Mariners did launch a fine number of homers opposite southpaws to rank 25th in team OPS (.363), but that also came with a lot of strikeouts. Once every 3.45 at-bats with a left-hander on the hill, they went down via the K, and that’s a really unhealthy rate for an offense.

With basically the same lineup other than Rowdy Tellez (who hits from the left side), this is a trend that figures to emerge once more. We may find out early, as the Mariners will take on a left-handed starter tonight for the first time this season.

Jeffrey Springs – now with the Athletics after being traded from Tampa Bay during the winter – gets the ball and is probably one of the most underrated southpaws in the game.

The 32-year-old holds a rather impressive 3.39 ERA in 145 career games (313 2/3 innings). People forget that Springs was fantastic as soon as he became a full-time starter with the Rays, first notching a 2.46 ERA in 33 games (25 starts) for them three years ago. Unfortunately, after a marvelous beginning to his 2023 season, Springs got hurt and had to undergo Tommy John surgery, thus costing him the rest of that year.

Springs returned last season and spun some of his usual quality work with a 3.27 ERA and 10.1 K/9 in seven starts, spanning 33 innings, before being shut down in September due to left elbow fatigue.

By all accounts, the eight-year veteran is fully healthy and can hopefully resume what he was doing previously: evolving into a potential All-Star starting pitcher. We’ll try banking on Springs exploiting his first opponent’s tendency to struggle against lefties.

The counterpart, Luis Castillo, enters his ninth season in the bigs after showcasing another solid body of work in 2024. Castillo did finish with a losing record (11-12), but his numbers were still good, reaching the 175-strikeout plateau for the fourth time in his career while posting a sub-1.20 WHIP for the third straight season.

His first assignment of the new campaign matches him with a familiar foe that he’s had success against since being traded to the Mariners three years ago. In fact, in seven meetings with the Athletics, he’s 4-2 with a 3.24 ERA, 1.10 WHIP and 9.9 K/9.

Additionally, the A’s managed only a .235/.283/.392 slash line in those meetings. The team’s Nos. 1-3 hitters (Lawrence Butler, JJ Bleday and Brent Rooker) are a combined 2-for-15 (.133) off Castillo with six strikeouts.

Both bullpens are at least decent enough to trust for the full game here, and that’s what we’ll go with in trying to land a low final score.

Pick: UNDER 7 (-108, DraftKings)

2025 MLB Over/Under Betting Record: 1-0, +1 unit
Yesterday’s Result: Pirates-Marlins F5 Under 3.5 (WIN)

Each bet is graded as if it were to win one unit unless otherwise stated.

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