Fun Differential Rolls continues in Seattle

This has not been the year of the AL West. With the reigning World Series champion Rangers sitting below .500 amid a series of injuries, the Astros' total aging, and the Angels and A's sitting low, one of baseball's strongest divisions of the past few years has weakened considerably. Just one team with a winning record: the Seattle Mariners. At 43-31, the Mariners hold an 8.5 game lead in the West, as some of the numbers below show that the team is not as good as its record suggests. Seattle bested its Pythagorean record by four wins and its BaseRuns record by two, and its run differential is the worst among the division leaders. But this kind of thing is not new to this organization.

The Mariners are currently enjoying their fourth straight year, falling short of a Wild Card berth in 2021 and '23 and snapping their decade-long playoff drought in '22. In all of these seasons, they have produced winners in close games like no other club, and manager Scott Servais has pointed to the composure and experience with which his side handle tight games. Famously, after a 2021 road trip in which the Mariners went 6-2 despite being shut out by their opponents, Servais introduced the term “fun difference” to evaluate the team rather than its worst difference. Three years later, with a new group of players, the exciting contrast is still at its peak.

Naturally, to win a lot of one-run games, you need to play in a lot of one-run games. One of the best ways to do that is to play a lot of low-scoring affairs, where neither team gets enough runs to keep their opponent away. And indeed, the Mariners rank in the bottom third of the majors in both runs scored and runs allowed. The first factor that gets them into so many games is the strength of their starting rotation, which has been among the best in baseball in both volume and efficiency. As a team, they rank eighth in ERA- and FIP-, and second in innings per start; They are one of only two teams to change the level starting in half time. While none of their starters dominate other boards, the depth they have is almost unmatched. The Mariners are one of three teams (along with the Phillies and Yankees) that have four professional starters with an ERA- of 95 or less, even with Seattle's fifth slot (started by Emerson Hancock, Bryan Woo, and Jonathan Diaz) included. up to a 3.25 ERA. In short, they are the only team in the league that can expect to start throwing the ball well every night.

On the other hand, Seattle's offense has taken a hit from last year. Lineage mainstays like JP Crawford, Julio Rodríguez, and Cal Raleigh have regressed this season, though Rodríguez turned things around last month. Most of the players Seattle added during the offseason also did not perform well. Returning fan favorite Mitch Haniger was below replacement level, and Jorge Polanco and Mitch Garver each hit below the Mendoza streak.

With an excellent rotation and below-average pitching, the Mariners have a recipe for low-scoring games, but there's another factor here: their home field. Mobile Park has been considered a pitcher's paradise since it opened 25 years ago, but it was less hitter-friendly in 2024 than in years past. Statcast's single-season park features him as the best park to pass pitchers this season, with an 87 rating; it has scored between 92 and 96 over the past half decade. The result is that nearly one-third of the Mariners' games have been decided by one run, one of the highest marks in the league.

Playing in multiple running games is one thing, but winning them is another. The Cubs and Athletics, the only teams with concurrent championships, each have losing records in such games. But the Mariners combined quantity and quality, having the most one-run wins while ranking second to the Rays in one-run percentage. In contests decided by multiple runs, the Mariners are 26-24 – their .520 winning percentage in such games is shockingly close to their .527 Pythagorean record – but the one-run win has put them a dozen games over .500. Some of these games came in dramatic fashion, as their five walk-offs tied for a team high. The Mariners were far from an offensive powerhouse, but all year the bats were alive when it mattered most.

These divorces are amazing. On a low level, the Mariners are one of the league's best hitters. But when the stakes are high, they collectively produce as the 15th best hitter in baseball. However, the eye-popping 144 wRC+ figure in highly rated positions comes with a .377 BABIP – more than 40 points more than any other team in that division. By the end of the year, that number will be lower than it is now, but if you look at the bottom, Seattle's hitters have still been hitting better than the average. Their three-point walk rate is higher and their three-pointer rate is lower in such situations, and their strikeout rate is also modestly higher.

While the Mariners' hitters may not be able to continue their dominance with dramatic moments, the production they get from their bullpen, another part of their success in the one-run game, is very consistent. Despite some confusing trades, a strong drop in assists has been a strength of Seattle's team of late. The organization has the ability to detect, locate, and develop under-the-radar weapons.

Andrés Muñoz is enjoying his first full season as the Mariners' closer, but he hasn't been put in save situations just for the ninth inning. In fact, only half of his appearances have started in the top of the ninth inning. He was called upon to pitch more than a few innings, but his most notable performance came when he pitched a dirty eighth inning and turned the save into four or five outs. Muñoz has recorded more than three strikeouts in seven games, second only to Mason Miller among full-time closers, and in those games, he has not given up one. Servais has been picking the right time to get his help on the mound, as Muñoz has the highest slugging percentage in the league.

Veteran reliever Ryne Stanek and 31-year-old Tayler Saucedo, who ranked above their closers on the leverage index leaderboard, handled most of the pitching duties ahead of Muñoz. The two complement each other well, as both Stanek, a righty, and Saucedo, a lefty, have significant platoon separation, and Servais uses them wisely based on matchups.

Among Seattle's junior options, first basemen Austin Voth and Trent Thornton have made strides out of the bullpen; the duo led the staff in relief innings while keeping runs off the board.

It would be easy to chalk this all up to luck, even within the context of some of the Mariners' recent teams. Their offense has less upside than in years past, and their bullpen relies more on top studs than the rest of the stable. However, they still have the ingredients that made them so successful in tough games, even if the recipe is slightly different. Besides, maybe a little diversity is a good thing. After all, in recent years the best the Mariners could do was secure one AL Wild Card spot. Now, for the first time in their happy split season, they are in a position to ride their recipe for success until they get the split crown.