MLB's scandalous strike zone change has good news, bad news for Mariners

Major League Baseball has a new strike zone in 2025, and the Seattle Mariners should be livid and excited about it.

This will make more sense in just a minute, but the first thing to know is that it is not due to a rule change that the strike zone is different. As reported by Jayson Stark, Ken Rosenthal, and Eno Sarris of The Athletic last week, MLB and the Major League Umpires Association agreed to a change over the winter in how umpires are evaluated.

In practice, they now have a smaller margin for error when their ball and strike calls are assessed by the league. In effect, this is resulting in a smaller strike zone even though the zone itself is technically the same.

It's all there in the numbers, courtesy of Baseball Savant. In 2024, 5.9 percent of all takes outside the strike zone were called strikes. In 2025, that figure has plummeted to 4.7 percent.

MLB's new strike zone is hurting Mariners pitchers, but helping Mariners hitters even more

As you would expect, Mariners pitchers are not being spared from the shift to a smaller strike zone. Here's how their rate of called strikes outside the zone has changed from 2024 to 2025:

• 2024: 6.5 percent
• 2025: 5.5 percent

It's a tough break for Mariners pitchers, generally, and for catcher Cal Raleigh, specifically. It was largely because of his framing skills that Mariners hurlers got strikes outside the zone at a 6.5 percent clip in 2024, which was the fifth-best rate in all of MLB.

Though it is not the reason — injuries to Logan Gilbert and George Kirby and Luis Castillo's advancing age haven't helped — it is certainly a reason that Mariners pitchers are among the biggest losers in strikeout rate from 2024 to 2025. Theirs is down 3.3 percent, the third-biggest drop in the league.

It is some comfort, however, that this is an equal-opportunity shift. Out of the 30 teams in MLB, only the Athletics are seeing their pitchers get more strikes outside the zone than they did in 2024. The other 29 are all in the red, and the Mariners' drop doesn't even look that bad compared to the 2.3-percent drops that the Kansas City Royals and Washington Nationals are experiencing.

Meanwhile, here's how the rate of called strikes outside the zone has shifted for Mariners hitters:

• 2024: 5.6 percent
• 2025: 4.4 percent

To this end, Mariners hitters have gained more from the new strike zone than the club's pitchers have lost. And it is making a difference, as the Mariners' offense is among the biggest 2024-to-2025 improvers for strikeout rate (-5.2 percent) and walk rate (+1.8 percent).

These improvements wouldn't necessarily be happening without the new strike zone. Seattle hitters aren't especially disciplined, ranking in the bottom half of MLB with a 28.3 out-of-zone swing rate. Nor are they especially good at making contact, as their 74.9 percent contact rate ranks ahead of only three other teams.

This is not to ignore the offensive revolution that has happened under manager Dan Wilson, but it feels like a happy accident that the strike zone got smaller just at a moment when the Mariners began shifting their run-scoring focus away from the home run and more toward a holistic style, with emphases on working good at-bats and putting the ball in play.

Ultimately, the Mariners are experiencing the best of both worlds. Though their pitchers aren't benefiting from the new strike zone, they're still 12th in ERA at 3.74. The offense, meanwhile, is fourth with an output of 5.1 runs per game.

These two things have led the Mariners to a 20-14 record that has them in first place in the American League West. So on balance, they probably shouldn't be wishing that MLB would go back to its old strike zone.