The Mariners are calling up Kade Anderson to make his MLB debut on Saturday against the Cubs, reports Jeff Passan of ESPN. Bryan Woo had been slated to start that game and will be presumably be pushed back to Sunday.

Seattle will need to make an active roster move involving a pitcher. They’ll also need to open a spot on the 40-man roster, but they can do that by transferring Matt Brash to the 60-day injured list without impacting his timeline. Brash has already missed more than 60 days with a lat strain.

President of baseball operations Jerry Dipoto teased an Anderson promotion earlier this month, saying they’d only do so when a rotation opportunity arose. “We’re not going to put Kade in the bullpen. He’s the best starting pitcher in the minor leagues,” Dipoto said in early August (link via Daniel Kramer of MLB.com). He went on to call Anderson “the next starter up” behind their front five after the M’s traded Luis Castillo to the White Sox.

This probably points to the Mariners adopting another six-man rotation. They’re not dealing with any injuries to their starting five. George Kirby and Bryce Miller have each gotten knocked around this month, so the M’s could kick one of them to the bullpen if they wanted to stay on a five-man schedule, but that’d be a surprise given their respective track records.

Anderson is viewed by most evaluators as the best pitching prospect in the game. Keith Law of The Athletic ranked him the #1 overall prospect in his most recent update shortly before the trade deadline. Seattle nabbed the 6’2″ southpaw with the third overall pick in the 2025 draft. He didn’t pitch professionally last year after throwing 119 innings in his sophomore season at LSU. The M’s assigned him to Double-A Arkansas this year and, as Dipoto mentioned, he has completely dominated the level.

In 18 starts, Anderson sports a 1.06 earned run average with a 41% strikeout rate. He has the best strikeout rate and ERA among all minor league pitchers with at least 80 innings. He’s coming off four consecutive scoreless outings while holding opposing batters to a laughable .147/.183/.216 slash line in 333 plate appearances.

Double-A hitters clearly can’t touch Anderson. Seattle is content to jump him past the hitter-friendly Pacific Coast League and test his stuff against MLB competition. Anderson has advanced command of a four-pitch mix (fastball, changeup, curveball, slider) that all rate as above-average to plus offerings. He’s viewed as a potential top-of-the-rotation starter.

Seattle has been among the game’s best teams at developing college pitchers. Their entire current rotation came via the draft and development route. Miller and Woo were mid-round selections, while Anderson joins Kirby, Logan Gilbert and Emerson Hancock as former first-round picks in the rotation. It’s one of the strongest groups in the majors on paper, but it has joined the offense and bullpen in underperforming of late.

Mariners starters entered Thursday’s game with a 4.46 ERA since the All-Star Break, the eighth-worst mark in the majors. Kirby got shelled for six runs in 3 1/3 innings in today’s loss in Milwaukee, which won’t do that mark any favors. It also dropped Seattle back eight games below .500 at 60-68, an astonishingly bad mark for a team that was one game away from the franchise’s first trip to the World Series a year ago.

That at least raised some question about whether the M’s would abandon their plans to call Anderson up this season. He would not have been eligible for the Rule 5 draft. The Mariners could’ve opted to keep Anderson off the 40-man roster and preserve his eligibility for minor league play in 2027 if the lockout results in cancelled MLB games. They’ve opted not to go that route, hoping Anderson can help turn their fortunes around this year.

The general mediocrity of the American League is the only reason the Mariners aren’t completely buried. They’re in third place in the AL West, 4.5 games behind the Astros and 2.5 back of the Rangers (pending those teams’ games on Thursday). They’re three games behind a 63-65 Twins team that now holds the last Wild Card spot, though there are five teams between them and Minnesota.

Seattle waited long enough in the season to preserve Anderson’s rookie eligibility going into 2027. He’d be eligible for the Prospect Promotion Incentive next year. If he breaks camp (or is called up by the middle of April), he could net them a draft pick down the line by either winning the ’27 Rookie of the Year award or finishing top three in Cy Young balloting within his first three full seasons. Anderson won’t be eligible for arbitration until the 2029-30 offseason and is under club control through the ’32 campaign if the service structure is unchanged in the next CBA.

Image courtesy of Steven Branscombe, Imagn Images.