How the underdog Athletics became the Mariners' biggest AL West threat

The Seattle Mariners are in first place in the American League West in large part because they have bullied other teams within the division. They are 11-4 against AL West foes, with wins in four of the five series they've played.

The one exception? A season-opening split against the team they'll take on in Sacramento over the next three days.

It might already feel like another lifetime ago, but the Mariners began their 2025 campaign by splitting a four-game set against the Athletics at T-Mobile park. It was a frustrating offensive series for the M's, who scored just eight runs in the four games.

The offense and the team in general have obviously fared much better since then, as the M's have averaged 5.9 runs per game amid a 17-6 run since April 7. And yet, that they have just a 2.0-game lead in the AL West speaks to how well the A's have kept pace.

Why the Athletics, not the Rangers or Astros, pose the biggest threat to the Mariners in the AL West

Mariners fans of a certain age might remember when the A's were similarly a thorn in Seattle's side in 2001. Though that was the year the M's won an AL-record 116 games, they barely won their season series against the A's and ultimately saw a 21-game lead in the AL West get reduced down to "just" 14 as the then-Oaklanders finished with 102 wins.

To be sure, we're probably not looking at a pair of 100-win behemoths that are destined for another showdown for the ages. But as the Mariners have clearly established themselves as a credible contender for AL West superiority, the A's have also been doing so in a sneakier fashion.

The A's come into this week's series having won 13 out of their last 19 games, and they tick in much the same way that the Mariners tick. Nobody was especially high on their offense at the outset of the year, yet it's proving to be a formidable unit.

The A's are tied with the Mariners as far as having the biggest improvement in strikeout rate relative to 2024, and are likewise among the biggest gainers in batting average, on-base percentage and slugging percentage. Their 110 OPS+ puts them ahead of even the star-studded Philadelphia Phillies.

The Mariners learned the hard way last year (i.e., 4 HR) that Brent Rooker was not to be taken lightly, and images of Tyler Soderstrom going off for three homers in this year's opening series are still burned into the club's retinas. Lawrence Bulter and Shea Langeliers are also fearsome sluggers, while rookie shortstop Jacob Wilson has gotten plenty of attention as he's pushed his average to .333.

Despite expectations to the contrary, it seems the A's (ostensibly temporary) new digs are a bit of a launching pad. Teams collectively have a .786 OPS at Sutter Health Park, the second-highest in MLB after Oriole Park at Camden Yards.

Paradoxically, though, this may bode better for the Mariners than for the A's. The A's only have a .722 OPS at home, compared to a .747 OPS on the road. At .804, the Mariners have the highest road OPS in the American League.

The A's also have a relatively vulnerable pitching staff that has gotten creamed in Sacramento, posting a 5.29 home ERA that ranks ahead of only the Baltimore Orioles and Colorado Rockies.

It nonetheless does not feel like an accident that it's the A's chasing the Mariners, and not the Texas Rangers or Houston Astros. There's all sorts of "fallen empire" energy emanating from the Texas franchises. For their part, that the A's are surging after daring to invest in an exciting roster is kind of a "duh" outcome.

As of now, FanGraphs has the Mariners as a 54.8 percent favorite to win the AL West. The A's are a 6.5 percent underdog, but their odds are rising and they already know from experience that they can hang with the Mariners.

If they do so again in this series, what's already a close race will between these two teams will suddenly look mighty interesting.

Game Times and Probable Pitchers for Mariners vs. Athletics, May 5-7

• Monday, May 5 at 7:05 p.m. PT: Bryce Miller vs. Luis Severino
• Tuesday, May 6 at 7:05 p.m. PT: Emerson Hancock vs. Jeffrey Springs
• Wednesday, May 7 at 12:35 p.m. PT: Bryan Woo vs. Gunnar Hoglund