Mariners' Wild, Fun and Potential Playoff 2021 Season Is Just the Beginning

If Major League Baseball's 2021 regular season had ended Wednesday, the Seattle Mariners would not have been headed for the playoffs. And if we're being frank, they're lucky to even be in the race heading into the season's final weekend.

But that's also the beauty of it.

Granted, a better word than "lucky" to describe the Mariners right now is simply "hot." They've won 10 of their last 11 games, 18 out of 26 in September and 41 of 68 in the second half.

What was a four-game deficit in the American League wild-card race as recently as Sept. 18 is now no deficit at all. The Mariners will begin their final three-game set against the Los Angeles Angels tied with the Boston Red Sox for the second spot.

Just one more win will secure the Mariners' first 90-win campaign since 2003. If other stars align just right during the season's final weekend, the organization could clinch its first playoff berth since its historic 116-win season in 2001.

According to FanGraphs, however, Seattle's chances of nabbing a wild-card slot are less than 30 percent. To the extent that the Mariners aren't really as good as their 89-70 record, this isn't an entirely unfair assessment.

What it misses, though, is the not-so-secret ingredient that's taken the Mariners this far. And no matter what happens, 2021 is merely the opening salvo of the latest dynasty in the Pacific Northwest.

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The Mariners Aren't (Traditionally) Good

Understanding the 2021 Mariners requires understanding fun differential.

This is not a typo, and not to be confused with run differential, which is where the Mariners aren't even breaking even at minus-48. They could become only the 10th playoff team with a negative run differential.

Thing is, the Mariners just aren't particularly good at fundamental aspects of the game. Their defense rates negatively in outs above average, defensive runs saved and ultimate zone rating. And even amid the team's strong second half, the offense is 12th among AL clubs in weighted on-base average, while the pitching staff ranks ninth in ERA and 10th in FIP.

The Mariners, however, couldn't care less about their run differential; they much prefer the other kind.

"Someone told me that our run differential was minus-nine on this trip," manager Scott Servais said in August, according to Corey Brock of The Athletic. "But our fun differential was about plus-90. So we are going with that."

You could argue that "fun differential" isn't an actual thing, but, hey, it must be something since it's on Baseball Reference:

Screenshot courtesy of Baseball Reference

You could also argue that it's impossible to quantify how much "fun" a team has, but take a moment to consider how the Mariners are generally boring on bad days yet practically unbeatable on good days. As in, they're 11-28 with a minus-135 run differential in games decided by five or more runs—and 78-42 with a plus-87 run differential otherwise.

This is to say Seattle is good when it has to be, and never more so than when the pressure is on. This can also be quantified with "clutch," which rates the Mariners as the best club there is on offense and the second-best there is on the mound based on how they've performed in high-leverage spots:

• Offense: .362 wOBA, 1st in MLB
• Pitching: .284 wOBA, 6th in MLB

Looking strictly at the Mariners' offensive performance in high-leverage spots, it's as if they've had Starling Marte (who also has a .362 wOBA) at the plate whenever they've needed a big hit. Accordingly, they've produced a lot of those this season.

This makes for at least one reason to believe the Mariners could pull off an improbable, 2006 St. Louis Cardinals-style run through the postseason if they can get in. Because under the bright lights of October, every situation might as well be a high-leverage situation.

Of course, this is an act we've seen from the Mariners before. Getting the job done in the clutch was also their M.O. in 2018, when they won 89 games despite a minus-34 run differential. It's perhaps a cautionary tale that those Mariners not only missed the playoffs but were also then promptly torn down ahead of a 94-loss season in 2019.

But if ever there was a case of "one of these things is not like the other," it's the 2018 Mariners vs. the 2021 Mariners.

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This Is Just the Beginning

Though the '18 Mariners were good in their own way, the future of that team never looked especially bright. Heck, with baseball's oldest offense and its worst farm system, that team basically didn't have a future.

By contrast, the '21 Mariners have one of the league's youngest offenses and a farm system that MLB.com ranked No. 2 overall. And if anything, these things undersell the team's youth movement.

Among AL clubs, the Mariners have given more plate appearances to 25-and-under hitters than every team except Cleveland. This is true even though reigning AL Rookie of the Year Kyle Lewis (knee) and Gold Glove first baseman Evan White (hip) have barely played because of injuries. Likewise, it only includes 241 plate appearances for 24-year-old second baseman Abraham Toro, who came aboard via trade in July.

While his performance as a rookie—i.e., a .177/.260/.349 line in 90 games—is alarming, 22-year-old center fielder Jarred Kelenic still has a lot of time to live up to his recent billing as one of baseball's 10 best prospects. To this end, the .903 OPS, 38 home runs and 41 stolen bases he's posted in three minor league seasons remain a tantalizing tease.

AP Photo/Ted S. Warren

By early 2022, Julio Rodriguez should also arrive. The power-hitting outfielder, who will turn 21 on Dec. 29, is in the No. 2 slot of MLB.com's top 100. He's slashed .347/.441/.560 in the minors this year, though that doesn't count his 1.069 OPS for the Dominican Republic's Olympic squad.

In the meantime, the Mariners have a Gold Glover at shortstop in J.P. Crawford and a young catching tandem in Luis Torrens and Cal Raleigh. Factor in the underrated Ty France and the potential returns of sluggers Kyle Seager ($20 million club option) and Mitch Haniger (free agent after 2022), and the developing picture is one of a lineup whose best days lie ahead.

Pitching-wise, the Mariners are set to return at least two solid starters in Chris Flexen and Marco Gonzales, and maybe a third if they exercise (and this is admittedly oversimplifying it) a four-year, $66 million option on All-Star Yusei Kikuchi. What they need is top-of-the-rotation talent, but they have options.

A former top prospect in his own right, Logan Gilbert has dazzled with his fastball velocity and walk rate, which rank in the 79th and 87th percentiles. He's also recently taken on the look of a Game 1 starter, ripping off a 2.70 ERA in six September outings.

Seattle likewise has right-handers George Kirby (No. 33 overall) and Emerson Hancock (No. 34) rising through its farm system. As its long-term books are essentially empty, the team also has the flexibility to seek a top-flight arm such as Robbie Ray, Kevin Gausman or even Max Scherzer in free agency.

Where the Mariners are now is similar to where the Toronto Blue Jays were last year. Sure, they've perhaps arrived ahead of schedule. But they're nonetheless here to stay, and their presence is likely only going to get bigger as they continue to develop their core.

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The AL West Is About to Become Very Winnable

Unlike the Blue Jays, however, the Mariners shouldn't have to worry about bumping up against insurmountable obstacles within the AL West.

Come the offseason, the division-leading Houston Astros will stand to lose shortstop Carlos Correa and aces Justin Verlander and Zack Greinke via free agency. And with MLB.com's No. 29 farm system, they might even be tempted to turn their focus to the future.

The Oakland Athletics, meanwhile, are about to lose a whole bunch of players in free agency. Plus, Matt Chapman and Matt Olson are at that point where their escalating salaries are clashing with Oakland's perennially limited budget. One of them might have to go in a trade so the A's can save money and bolster their 28th-ranked system.

In Anaheim, just how the heck the Angels are supposed to break out of a string of six straight losing seasons is a good question. At the least, they'll need to add a whole bunch of pitching. After that, they'll need to hope that Mike Trout's and Anthony Rendon's injury-ruined 2021 seasons aren't a sign of things to come.

The Texas Rangers? Well, what about the Texas Rangers? They're second to only the Baltimore Orioles in losses over the last two seasons. Their rebuild likely has at least two or three seasons to go before it's done.

So even if the Mariners aren't the best team in the AL West right now, they're the only team in the division that is heading upward. As long as that's the case, 2021 will be neither their last nor their best chance to finally break their playoff drought.

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Stats courtesy of Baseball Reference, FanGraphs and Baseball Savant.