Why Mariners' recent offensive demise in May was entirely predictable

Last season was mostly a nightmare for the Seattle Mariners offensively. They ranked just 21st in scoring, highlighted by leading the majors in strikeouts and having the second-worst team batting average. However, hope came courtesy of the hiring of Dan Wilson as manager, with the lineup performing wonders and scoring the third-most runs in baseball during September.

This resurgence spilled over into this year as the Mariners showed that Wilson's offensive approach was, while different, also the real deal as explained by Tanner Vogt. In fact, this approach resulted in a record-setting start to 2025, with the M's becoming the only team in MLB history to tally at least 40 home runs, 30 stolen bases, and 130 walks within the first 30 games of a season.

A noticeable demise in offense and wins for the Mariners

Unfortunately for the Mariners and their fans, things have not gone quite as well offensively since the calendar flipped from April to May. After producing a .754 OPS in March/April, they entered Tuesday's series opener versus the Washington Nationals with a .680 OPS for the month of May — a 74-point swing in the wrong direction which was the biggest of any AL team.

This has in turn been reflected in the Mariners' record, which was 18-12 at the conclusion of April and had them sitting just 0.5 games behind the Detroit Tigers for top spot in the American League. However, they entered the Nationals series with a .500 record for May at 11-11, and 4.5 games back of the Tigers at the AL summit.

So what's happened to the offense to result in a downturn in the Mariners' fortunes? Among other things, the walks have dried up since the team rose to the top of the majors in this category, they've been striking out more of late, and an aggressive approach in respect of stealing bases has not been nearly as frequent.

Mariners' slump was almost expected

In fairness to the Mariners, their offensive slump was well overdue for a number of reasons. These include the injuries to Víctor Robles and Luke Raley, which were bound to hurt the team eventually. Robles was an offensive spark plug after arriving in Seattle last June but is potentially done for this season, although the versatile Raley at least has the opportunity to return sometime during next month.

Another factor which has played into the offensive regression is Jorge Polanco, who was never going to stay as hot as he was, but has still fallen more spectacularly then envisioned. At the end of April he had a stunning 1.226 OPS and 260 wRC+ while batting .384, compared to .476, 43 ,and .155 respectively so far in May.

It's not all bad news for the Mariners offensively, specifically with the likes of Cal Raleigh, Julio Rodríguez and Randy Arozarena all being bright spots. Raleigh has been consistently productive throughout, Rodríguez is undergoing his usual warmup as the season progresses, and we're mostly seeing the positive side of Arozarena's mercurial talent.

The overriding issue is that this cast of characters is ultimately very similar to the one which struggled offensively throughout most of 2024. It is a thin lineup below the stars, featuring inconsistent/undewhelming hitters such as Mitch Garver, Donovan Solano and Miles Mastrobuoni.

Overall, though, we retain belief that Wilson's offensive philosophy can help overcome any lineup shortcomings, at least to a certain extent. As such, we do not anticipate the current offensive slump to continue indefinitely, but at the same time will warn that there's a strong chance the lineup won't quite return to the level it collectively performed at during March/April.

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