The Mariners have dominated one-run games, and all explanations but Edwin Díaz are inconclusive

Have you heard the rumblings? It’s about the Mariners, and their one-run games. They win them often, which is not typically what is done. At 26-11 in one-run games, they won’t challenge the Rangers’ all-time record of 36-11, but they’ll almost certainly lead 2018 in one-run wins. They’re 23 games over .500 with a +22 run differential! Jeff Sullivan wrote about them today, covering much of what I was intending to highlight, which is the danger of writing about the Mariners doing interesting things. Jay Jaffe wrote about them a few weeks ago. as well, which led me to a 2013 study by Jesse Wolfersberger, and now you’re all caught up. Within that study, Wolfersberger uncovered something interesting about the nature of one-run wins:

The goal is to better determine how much of one-run record is skill, and how much is still unexplained ... The resulting model showed that there are certain team attributes which lend themselves to better records in close games. However, the model had limited explanatory power. There were only three significant coefficients: isolated power for hitters, and strikeouts per nine and walks per nine of relievers. This means that those three variables are the most important for explaining a team’s one-run winning percentage.

Reliever K/9, reliever BB/9, and hitter ISO (aka power numbers, ISO = SLG-BA) are what appeared as separating variables for teams that consistently exceed their expected production in one-run games. As Wolfersberger notes in his article, there’s much more that goes into the equation of “clutch.” It’s a neat little framework, however, so I wanted to see if the Mariners fit the mold of this “expected” one-run game overachiever.

First I tracked down the team’s overall numbers in these areas, as well as reliever K/BB. Then I looked at the Mariners’ performances from the 7th inning thru the 9th and extra innings. It’s an imperfect whittling, but it felt appropriate offensively to isolate where the Mariners had been making their hay. Finally I also included their numbers in high leverage situations.

The M’s have been among the best in the league with the game in its final innings. Their bullpen, and Edwin Díaz in particular of course, grade unsurprisingly well. The power numbers, however, don’t jump off the page. They’re better than league-average, but not drastically... until high-leverage situations. Is that a skill? Considering their otherwise average offensive power numbers, it’s tough to grant the benefit of that doubt.

Seattle’s performance in late-game situations, and when it’s been needed most, has been among the best in league. If they performed the way they did in “clutch” situations over the course of entire games, they’d boast a far more impressive run differential and likely draw far less skepticism.

Unfortunately, they don’t.

Seattle’s lack of offensive black holes may help them produce consistently competitive plate appearances in late-game situations. The fact that the angel of death is their closer definitely helps, but by what we can easily track it’s difficult to credit Seattle’s late-inning production as something systemic. Their contact-heavy style may allow them to better handle high-velocity relievers. Seattle owns a .341 wOBA against pitches at 95 mph or harder from the 7th inning on (5th-best in baseball) but once again that dominance hasn’t persisted throughout a full game, as they’re maintaining just a .306 wOBA against such pitches overall. What we know is that Edwin Díaz, while not a candidate for MVP of the league, is the best bet to keep the Mariners’ magical season rolling.