The Mariners understandably upset their fan base on Wednesday when, while just one game out of the Wild Card race, they traded away Kendall Graveman, and to the Astros no less. While it’s still a debatable move, Seattle general manager Jerry Dipoto has shown a bit more of his hand since; after trading for Tyler Anderson to stabilize the rotation on Wednesday night, he found a better reliever than Graveman in the form of Rays closer Diego Castillo, who was acquired for righty J.T. Chargois and minor league corner infielder Austin Shenton. For Seattle, mystery solved, at least kind of; for the Rays, on the other hand, it’s a curious decision.
In getting Castillo, the Mariners have upgraded their late-inning options for the stretch run. Armed with one of the more deadly two-pitch combinations in the game, he is throwing more strikes than ever and missing more bats than ever, and given that he’s just 27, there’s still upside beyond what we’ve seen. There’s nothing complicated about what Castillo does or the way he does it; he’s a classic let-it-eat bullpen ace who sits 96–98 mph with the heater and has a slider in the upper-80s. In an era obsessed with revolutions per minute, he is the rare anti-spin guy, with below-average RPMs on both offerings, but he has found a way to add some two-plane break to his breaking ball this year. He’s also using his slider more than ever in 2021, with nearly 70% usage. Compare that to just two years ago, when he went after hitters with a nearly 50/50 mix.
While Castillo has greatly reduced his walks, he still certainly has far more control than command. It’s the same approach against every hitter: he elevates his fastball and throws his slider to the one location he can consistently get to, working the lower outer edge to right-handed hitters and back-footing lefties. It’s the kind of thing you can succeed at with quality pitches, and there’s no reason to think that success won’t continue. The Mariners added an elite high-leverage reliever who should be able to rack up saves in the Emerald City for three more years (Castillo is arbitration eligible for the first time this offseason), and they made their big league roster better, both right now and in the future.
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