Kade Anderson’s season at Double-A Arkansas was the kind of run that forces people to stop and take notice.
The 22-year-old Mariners left-hander was called up to Seattle on Aug. 22, and that promotion likely keeps him from qualifying for the minor league ERA title. Even so, what he put together over 18 starts and 93.1 innings stands out on its own. In fact, by ERA alone, it may be the best minor league season in years.
Anderson finished with a 1.06 ERA, which ranks as the second-lowest mark for any pitcher with at least 90 innings at Double-A and/or Triple-A since 1963, according to help from Dan Hirsch at Baseball-Reference.com. The only pitcher ahead of him was Mickey Scott, a 26-year-old left-hander who logged a 0.99 ERA in 91 innings for Triple-A Rochester in 1974.
Zoom out a little further, and Anderson’s numbers still land in rare territory. Since the minor leagues were reorganized in 1963, his 1.06 ERA is the eighth-best single-season mark for any pitcher with at least 90 innings in an affiliated minor league or leagues.
What makes it even more striking is the environment he did it in. Run scoring in the minors has been at historic levels this season, with the overall rate sitting at 5.52 runs per game, the highest mark since at least 1988, when Baseball America’s complete records begin. The overall minor league ERA this year is 5.15, while it’s about 5.00 at the full-season level and in the Texas League, where Anderson pitched exclusively.
Adjusted for league context but not ballpark, Anderson’s ERA translates to a 472 ERA+. In plain terms, that means he was 372% better than the average Texas League pitcher and nearly 400% better than the average minor league pitcher overall.
The Mariners made Anderson the No. 3 overall pick in 2025, the same year he led LSU to a College World Series title as the Tigers’ ace. His success has always come from a mix of command, control and a four-pitch arsenal he knows how to use.
At Double-A, Anderson threw strikes 69% of the time and worked his 93-94 mph fastball to all four corners of the zone. He paired it with secondaries that he placed with real precision: a low-80s changeup down and arm side, a mid-80s slider down and glove side, and an 80 mph curveball that he dropped across the bottom of the zone.
Anderson wasn’t just getting outs; he was missing bats and avoiding free passes. He led all Texas League starters with a 40.5% strikeout rate and a 3.9% walk rate.
Even so, the best pitcher to emerge from that Arkansas rotation might not be the one with the eye-popping ERA. Right-hander Ryan Sloan didn’t match Anderson’s statistical dominance, but he is two years younger. Sloan posted a 3.75 ERA with 100 strikeouts and 14 walks in 81.2 innings.
Scouts who like Sloan point to the raw stuff: a 95-97 mph fastball that can reach 100, a hard cutter, a sharp sweeper and a changeup that is still coming along. Some believe that once he matures and sharpens the package, the 20-year-old could wind up as the better big league pitcher.
Either way, the Mariners have reasons to feel good about what they’ve got coming through Arkansas. No matter which of the co-aces you prefer, the organization looks set to keep one of baseball’s strongest rotations stocked for a while.
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