The numbers behind the Seattle Mariners’ two-month slide

The Seattle Mariners are in the midst of a devastating collapse over the past two and a half months.

Mariners in a nightmare spot as September begins

On June 18, the Mariners were 44-31. They held a commanding 10-game lead atop the American League West, which marked their largest division lead since 2001. They had the fourth-best record in the AL and the eighth-best record in the majors. Their starting rotation was so dominant that, even with a sputtering offense, they looked like legitimate World Series contenders.

Then came a disastrous free fall.

Since that high-water mark on June 18, the Mariners have gone 25-39. That’s the second-worst record in the majors over that span – ahead of only the Chicago White Sox, who at 31-109 own one of the worst records in MLB history. The M’s now trail the Houston Astros by 6.5 games in the AL West and sit 5.5 games out of the AL’s final wild-card spot. Over the past two and a half months, their Fangraphs playoff odds have plummeted from 91.7% to just 4.6%. And things got so bad that they relieved manager Scott Servais of his duties last month.

Obviously, the vast majority of the Mariners’ problems are rooted in their struggling lineup, which ranks at or near the bottom of the majors in nearly every major statistical category. However, their lineup was also near the bottom of the league for the first few months of the season. So what exactly has been different since June 18?

Here’s a closer look at some key team statistics. For each category, the first number is through June 18 and the second number is after June 18. The numbers in parentheses are where Seattle ranks among the 30 MLB teams over that span.

Seattle Mariners’ lineup

Runs per game: increased from 3.95 (24th) to 3.97 (27th)

Batting average: decreased from .222 (28th) to .208 (30th)

On-base percentage: increased from .302 (25th) to .305 (22nd)

Slugging percentage: decreased from .372 (22nd) to .352 (28th)

OPS: decreased from .674 (23rd) to .657 (28th)

Strikeout rate: increased from 27.5% (30th) to 27.6% (2nd)

The Mariners’ runs per game and strikeout rate have remained about the same through June 18 and afterward, while their batting average, slugging percentage and OPS have decreased slightly. Most notably, their .208 batting average after June 18 is 10 points worse than any other team over that span.

Bullpen

ERA: increased from 3.70 (15th) to 3.94 (14th)

WHIP: increased from 1.17 (4th) to 1.21 (9th)

Opponent batting average: increased from .213 (4th) to .219 (6th)

Save percentage: decreased from 74.2% to 38.9%

The bullpen has experienced a slight regression in ERA, WHIP and opponent batting average. However, the big difference is the group’s performance in close games. Through June 18, Seattle relievers had 23 saves and eight blown saves. Since then, they have had just seven saves and 11 blown saves.

Starting rotation

ERA: increased from 3.29 (4th) to 3.49 (2nd)

WHIP: increased from 1.01 (1st) to 1.06 (1st)

Opponent batting average: increased from .214 (2nd) to .231 (4th)

The starting rotation has been elite all season. The group’s stats have declined ever so slightly since June 18, but they are still firmly among the best in the league.

One-run games

Through June 18: 17-7 record

After June 18: 6-17 record

Here’s where the major difference lies. The Mariners excelled in one-run games over the first half of the season, but have struggled mightily in one-run games since then. That’s especially been the case lately, with Seattle having lost four consecutive games all by a single run – including three in walkoff fashion.

As the stats illustrate, the Mariners have been more or less been the same team all season long – an elite starting rotation, an average to above-average bullpen and an offense that’s among the worst in the league. That combination has resulted in a slew of tight, low-scoring games. For the first half of the season, statistical variance in those tight games was on Seattle’s side. In the second half, it’s been the opposite.

More on the Seattle Mariners

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• Seattle Mariners promote two pitchers as rosters expand
• Why Edgar has high hopes for Julio Rodríguez in final month
• Salk: Who can unlock Julio? Why Edgar Martinez has a shot
• Bowden: Why Seattle Mariners’ manager switch needed to be made

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