The Mariners’ Rotation Is Carrying Them Through Their Hot Streak

Robbie Ray
Joe Nicholson-USA TODAY Sports

On June 19, the Mariners lost 4–0 to the Angels. It was their second straight shutout loss, ending an 11-game homestand where they went 2–9, dropping them to a season-low 10 games under .500, and leaving their postseason odds at a minuscule 5.3%. Since then, they’ve gone 16–3 and tied the Blue Jays for the final American League Wild Card spot after sweeping them in four games last weekend, passing five teams in the standings during this hot streak and digging themselves out of a pretty deep hole.

As you’d expect for a team playing so well, Seattle has seen contributions from all across the roster. But the pitching staff has been particularly strong, leading the majors in ERA at 2.99 since the beginning of June — a period that includes that aforementioned horrible homestand. In that same span, the starting rotation has posted a 3.06 ERA, and from June 2 to 26, it put together a 24-game streak of allowing three or fewer earned runs. The group’s collective FIP and xFIP during this period are both more than a full run above their ERA, likely indicating some amount of good fortune, but any team that rattles off 16 wins in a 19-game stretch is bound to benefit from some luck. Still, despite the gap between their results and their peripherals, many of Seattle’s starters have made beneficial adjustments to their arsenals that have fueled a lot of their recent success.

Mariners Starters, Since June 1
Robbie Ray 49.2 3.24 1.99 3.67 3.51
Logan Gilbert 47 3.64 3.45 4.05 4.04
Marco Gonzales 43.2 1.33 2.89 4.62 5.00
Chris Flexen 39.2 1.93 3.40 3.44 5.08
George Kirby 38.1 5.67 3.99 4.94 3.67

It all starts with the reigning AL Cy Young award winner, Robbie Ray. Diminished velocity led to a rough first couple of months; through his first 11 starts of the season, his ERA was sitting just under five, though his FIP and xFIP both painted a more optimistic picture. Some of that likely had to do with his propensity to allow a bunch of runs in a single bad inning in nearly all of his starts. But in his start against the Astros on June 6, he made a change to his pitch repertoire, adding a sinker — a pitch that’s now become an integral part of his arsenal:

Last year in Toronto, Ray leaned into his four-seam fastball and slider as his two primary pitches. He continued that trend in Seattle to the point where he was essentially a two-pitch pitcher during the first two months of the season. Whether it was the diminished velocity or batters simply figuring out his approach, he wasn’t nearly as effective. By introducing a sinker into his mix (and throwing his curveball a little bit more, too), he’s given opposing batters a new wrinkle to figure out.

The results of that adjustment speak for themselves. Since adding the sinker, he’s allowed just eight total runs in his last seven starts for a 1.41 ERA and no more than four hits in his last six turns. The strikeouts are still there, too; his sinker has a 29.3% whiff rate, better than his four-seamer and the seventh-highest among all sinkers thrown at least 100 times this season. For a more in-depth look at how Ray is employing his new pitch, I’d encourage you to read this analysis by Michael Ajeto over on Baseball Prospectus. Here’s the most important takeaway:

Before, Ray located the fastball up and glove-side, and the slider below it, which meant that hitters mostly only had to look to two spots. With this sinker, Ray is creating room by expanding the zone horizontally.

Behind Ray, the Mariners have gotten some good performances from Marco Gonzales. A constant presence in their rotation through Seattle’s rebuild cycle, he suffered through an up-and-down season in 2021, with an elbow injury affecting his pinpoint command and leading to the highest full-season walk rate of his career. He ended the year with an ERA under four, but his FIP was nearly a run and a half higher than that. His groundball rate, meanwhile, had sunk to a career-low, as he allowed a ton of elevated contact and home runs.

This year, Gonzales’ walk rate is even higher, and his strikeout rate has collapsed to just 12.1%. So how has that added up to a 3.24 ERA? Rather than flooding the zone with his sub-90 mph fastball, he’s fully leaning into his ability to manage contact against him. His groundball rate has gone from a career-low 32.2% to a career-high 46.5%, with batters finding it very difficult to square up his pitches.

The biggest change in his pitch arsenal is to his changeup. His best offering throughout his career, he’s throwing it more often than ever and changed the shape of it as well, adding more than three inches of drop and more than an inch of arm-side break. It now has the sixth-most horizontal movement of any changeup thrown at least 100 times this year.

Ray isn’t the only pitcher in Seattle who has added a pitch to his repertoire mid-season. In his first season back in the States after a one-year stint in Korea in 2020, Chris Flexen was a solid innings-eating starter whose peripherals weren’t outstanding — just a 3.61 ERA and a 3.89 FIP — but who got the job done on most nights. Like Ray, he struggled through the first two months of this season; through his first 10 starts of the season, his ERA was 4.55.

On June 7, Flexen began throwing a slider, which essentially replaced his curveball in his pitch mix. The slower, loopier curve had been a key piece of his approach in Korea, but it just wasn’t good enough to fool major league batters, who were slugging 1.364 off that pitch this year. The slider is thrown a bit harder than the curve with a good amount of vertical movement. It’s worked wonders so far, with opposing batters collecting just two hits off the pitch, both singles, and whiffing 28.1% of the time against it. Since introducing the slider, Flexen has allowed just 12 runs in six starts and matched a career-high eight strikeouts in his last start against the Padres, which also happened to be the start with his highest slider usage.

Then there are the youngsters. Logan Gilbert has dazzled in his sophomore season after his up-and-down debut last year. He revamped all three of his secondary offerings during the offseason to find more consistency and better feel for them and wound up adding six miles per hour to his curveball and changeup and four miles per hour to his slider. His pitch mix is still fastball-heavy, but he’s locating his breaking balls in the zone regularly. Despite the improved stuff and better command of those pitches, each of them has been a little worse at generating whiffs this year. His fastball is still a monster, though, and with his elite extension, it’s a headache for batters to catch up to.

George Kirby debuted on May 8 and has shown off pinpoint command; among all starters with a similar number of innings pitched, his walk rate is the third-lowest in baseball. Like Gilbert, his pitch mix is fastball-heavy, with his secondary offerings lagging behind. Both of his breaking balls and his changeup possess excellent underlying traits, but that raw stuff hasn’t translated into results yet. It’s possible he’s filling the strike zone up too much and will need to use his excellent command to try to earn chases a bit more often.

The biggest concern with Kirby is his workload. Last year, he threw 67.2 innings between High-A and Double-A. He’s already surpassed that mark this season, forcing the Mariners to start managing his innings; on Saturday, they optioned him to Triple-A, where he’ll spend the All-Star break before coming back up after it. They can use roster machinations like that to limit Kirby’s innings this summer as much as possible, but if they want him to contribute to their playoff hunt in September and, hopefully, into October, they’ll likely have to push him hard at some point.

Most importantly for Seattle is that through all the unfortunate injuries and suspensions the lineup has had to endure, the starting rotation has survived the season relatively unscathed. The Mariners haven’t lost a single starter to injury yet, and those starters have thrown the third-most innings in the majors. Proportionally, Seattle’s starters have thrown the second-highest number of innings:

SP/RP Proportional Mix
HOU 752.2 489.1 65.02% 3.15
SEA 771.2 487 63.15% 3.59
SDP 789.1 498.2 63.14% 3.59
CLE 743.1 467.1 62.86% 4.16
PHI 773 481.2 62.25% 3.76
NYY 772 480 62.18% 3.23
MIA 750.2 464.2 61.88% 3.60

That amount of work has helped save the bullpen from becoming overtaxed early in the season. In fact, since June 20, the day this hot streak started, the Mariners’ relief corps has posted the lowest ERA and lowest FIP in the majors. Their relievers have struck out nearly a third of the batters they’ve faced during this stretch, with Paul Sewald (30.4% strikeout rate), Penn Murfee (31.8%), and Andrés Muñoz (40.2%) leading the way.

The Mariners will likely need to lean on their relief corps a little more as the season wears on, between the workload management for Kirby — and probably Gilbert, too — and the likely regression once their luck starts to match their peripherals. They could also look to add a flexible starter at the trade deadline who could soak up some of those innings during the dog days of August so the team can allow its youngsters to rest. There’s no guarantee the rotation will make it through the season without suffering a major injury, so adding to the depth should be a paramount concern this month.

This hot stretch has put the Mariners in position to make a serious run at an AL Wild Card spot. Just 18 of their remaining 75 games are against teams currently above .500, plus seven games against the Guardians, who are right at .500. Amidst that is a tough stretch after the All-Star break with seven games against the Astros and six against the Yankees in a three-week period, though the returns of Mitch Haniger and Kyle Lewis from the IL around that time should help. And after that gauntlet against the two best teams in the AL, it should be smoother sailing through the end of the season. All told, Seattle has the sixth-lowest remaining strength of schedule and playoff odds of 44.6% — the highest they’ve been since late April and a jump of almost 40 points since June 19. Mariners fans know better than most to hold any sign of hope loosely, but if the pitching staff can continue to shine, it certainly seems like Seattle is poised to break its infamous playoff drought.

Jake Mailhot is a contributor to FanGraphs. A long-suffering Mariners fan, he also writes about them for Lookout Landing. Follow him on Twitter @jakemailhot.

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Mitchell Mooremember
1 year ago

They need to do better than Flexen and/or Gonzalez if they expect compete with the juggernauts.

1 year ago
Reply to  Mitchell Moore

I think it’s impossible to underrate the difference just making the playoffs would make after 21 years of not doing that. If they play four playoff games and then go out that represents a complete reimagining of what the franchise is even possible of.

Or at the very least it does to me. I have no idea if that sentiment is particularly shared but “the Mariners win the World Series” is just a completely alien concept to me. It would simply be nice to see something *different* for once.

1 year ago
Reply to  Mitchell Moore

I’m actually not sure this is true — especially if they end up being the 4th/5th best starters. IMO Kirby has looked better so far than either, with the caveats above about innings of course.

I think the bigger risk is if, e.g., Gilbert and Kirby both get injured and then Marco Gonzales is your #2, that will be rough against the Astros or Yankees.