The Mariners are not the worst team in baseball anymore.
That hasn’t always been obvious these last few months. The Mariners have been terrible in the second half of the season. They’ve confirmed a losing record for the first time since 2021 and are all but eliminated from contention. In fact, they’ve been so bad one could fairly argue they were underdogs going into their recent series against the lowly A’s and Angels — they lost all three series. I even went so far as to say they were a push against the Rockies
over the weekend. And that wound up being a fair assessment. They won the series but walked away with an even run differential at 10 runs scored and allowed.
Still, I have to give credit where it’s due. The series did move the Mariners ahead of the Rockies by WAR since the All-Star break. They are now merely the second worst team in the majors in the second half:
Now, all of my league-worst doomsaying generally comes down to these WAR leaderboards. If we look at actual wins and losses, the Mariners are more like the sixth worst team in the majors in the second half, and not all that notable in a historic context. There’s reasons for this discrepancy, and WAR isn’t always the best at capturing the nuance in team-level performance in small (going on medium) samples.
But I think it’s worth understanding just how bad the Mariners look from this “true talent” perspective. This isn’t just a normal slump that every team goes through at some point in the season. This is the worst the Mariners have played in a half season this century:
The 2026 team is right there with the 2008 and 2010 teams by WAR in the second half. Again, both those teams lost far more games in either half, but it’s notable that the 2026 squad is comparable.
Now, “half” seasons are a misnomer. The split you see at FanGraphs or Baseball Reference simply denotes where the All-Star break divided the season in two, rather than equal 81-game stretches. For instance, the Mariners played 74 games in the second half of 2010, while they’ll only play 65 games in the second half of this year. In other words, on a rate basis, the Mariners aren’t nearly as bad in this second half as they were in those years.
Let’s account for this. I found every team’s half-season WAR and found the percentile and z-score within each half season. This way, we kind of sidestep the sample size question and think of these figures as relative to the rest of the league and half season. From that view, this is somewhere between the second and fourth worst stretch of baseball the Mariners have played this century.
What makes 2026 weird, of course, is the Mariners were actually pretty good in the first half. Sure, they were disappointing in many ways, but they ultimately ranked seventh in WAR and had a decent run differential. It wouldn’t have been surprising to see them surge in the second half, or at least maintain a frustrating relationship to .500. That would have been a totally normal shape for the season to take.
Instead, we got this:
Again, the Mariners are second worst team by WAR in the second half of 2026, behind only the Rockies. I looked into how rare it is for a team to collapse like this. In terms of raw WAR, the Mariners 16-WAR drop between halves is the ninth largest this century. That figure contains a few teams, like the 2018 Astros, who went from “best ever” to merely elite. If we instead look at change in z-score, the Mariners collapse is the sixth largest this century. And if we look at percentile change — i.e., the drop from seventh to 29th — the collapse is the third largest. We don’t see something like this every year:
That’s to say, no matter how you cut it, 2026 represents both 1) some of the worst baseball the Mariners have played this century, and 2) one of the largest collapses in true talent we’ve seen from any team this century.
The reason isn’t complicated. The Mariners have been dreadful — truly dreadful — on the mound. They have a total of 0.6 WAR from their pitching staff in the second half, which ranks last by nearly a full win. Their starters have posted 1.7 WAR (29th) and their relievers have posted -1.1 (obviously 30th). August was arguably the worst pitching month in team history, and the Mariners have never been outscored by more runs.
Of course, the reason the Mariners were competitive in the first half is because their rotation was the very best in the majors by WAR. And while the bullpen was always somewhat shaky, they could avoid their worst options by getting seven innings a night from their starters. They were a top five pitching group overall in the first half. It doesn’t matter how you sort it, this is far and away the largest pitching collapse this century. We’ve never seen such excellence followed by such… whatever you want to call it.
It’s hard to know exactly how much to blame the pitching, because the Mariners on defense are easily the worst fielding group in the majors in the second half. They were in the first half, too, but they’ve somehow gotten even worse. Since the All-Star break, they are in last by Fielding Run Value at catcher, third base, and shortstop. They are next to last at second base. The only position they’ve gotten positive value from is first base.
The Mariners lineup hasn’t even been that bad. They currently rank ninth by batting runs in the second half, with a broadly acceptable 103 wRC+. But for a team that largely punted defense to maximize offense, that’s not quite enough to reach even the median. The Mariners position players rank 18th in the second half by WAR, essentially unchanged from the first half.
I’ll leave you with a final plot:
This shows second half WAR (by z-score) on the x axis and next season WAR on the y axis. The Mariners second half WAR in 2026 is represented by the red line.
We can see a somewhat linear relationship between the points, meaning second half performance is generally indicative of next year performance. We can also see it’s rare for a team to play as bad as the Mariners have in the second half and then go on to be good, much less great, the next year. This is why the depth of the Mariners recent failure is concerning. What we’ve seen is not just bad baseball but a symptom of a bad baseball team. And it’s not easy to go from a bad baseball team to a good baseball team in an offseason.
That said, a bounce back is not without precedence. The only team this century to go from a bottom five team in the second half to a top five team the next year is the Red Sox. They did it twice, once from 2006 to 2007, and once from 2012 to 2013. They won the World Series both years.
