Mariners Get a Player Development Wake-Up Call as Athletics Poach Brewers Executive

We’ve admired the pipeline. Let’s see the plumbing work.

Feb 23, 2026; Scottsdale, Arizona, USA; Athletics shortstop Leo de Vries (83) prepares to play the San Francisco Giants at Scottsdale Stadium. Mandatory Credit: Rick Scuteri-Imagn Images | IMAGN IMAGES via Reuters Connect

The Athletics made a hire that should get Seattle’s attention. The A’s are hiring Cam Castro away from the World Series champion Milwaukee Brewers to become their general manager under president of baseball operations Taylor Smith.

The interesting part is what the A’s want from him. They want Castro’s ability to turn promising players into useful major leaguers. We’ve seen what the Brewers can do with their pipeline, and the A’s certainly are not short on young, promising talent.

We spend time admiring the next wave in Seattle. Eventually, those players need to make the team better. The A’s just brought in someone whose career has been built around that exact responsibility.

Athletics Are Buying the Development Results Mariners Need

Castro joined Milwaukee as a minor league pitching coach in 2019 and worked his way through pitching coordination and development before becoming senior vice president of player development and performance. His responsibilities included minor league development strategies, sports science and connecting development initiatives with the major league coaching staff. He also previously worked at Driveline in Kent. Which might sound familiar to Jason Kanzler and CJ Gillman’s background.

That connection adds a little local flavor. But besides that point, the A’s are hiring someone who has worked through the daily business of helping players improve and making sure the information coming from one department becomes something a coach can actually teach.

It’s a comparison the Mariners should welcome as they’re going through some of their own philosophical changes. An organization that puts this much faith in developing talent ought to be comfortable having its work judged by what those players eventually produce.

Mariners’ Development Promise Needs to Show Up in the Lineup

Seattle has already made its own investment in development experience, hiring former Cubs farm director Jason Kanzler as manager after a 76–86 season. Kanzler oversaw Chicago’s minor league system, its players and its coaching staff.

That makes the standard here pretty clear. The A’s are showing the confidence to overhaul their operation and bring in someone who can help them get more from the talent they already have.

And there’s plenty to work with. Nick Kurtz, Jacob Wilson and Lawrence Butler give them a young offensive core worth taking seriously, with Brent Rooker supplying established thump. Leo De Vries’ eventual arrival could make that group even more dangerous, though his recovery from shoulder surgery comes first.

Also, if they can get those hitters enough pitching support, the A’s will become a much tougher assignment for Seattle.

That’s where hiring Castro makes so much sense. Milwaukee figured out how to develop pitching within a smaller-market operation, and Castro helped oversee that work. The A’s are betting he can bring that expertise to an organization that badly needs the help.

Going after the reigning World Series champion’s development leadership was smart. If we’re talking about changing a culture and raising expectations, hiring someone who helped build a winner is a pretty convincing opening move. The A’s identified an operation worth learning from and went after one of the people responsible.

The financial fit also plays a big role. Castro comes from a club where developing affordable contributors is essential to keeping the team competitive. That experience should translate well to the A’s, where getting more from young players will be central to any lasting turnaround.

That should command a lot of attention in the AL West. The A’s have hitters worth building around, more talent coming and new leadership charged with fixing the pitching. Seattle has every reason to take that combination seriously.

Castro will have to prove himself in a new organization. Milwaukee’s championship doesn’t come packed in his moving boxes, and the A’s have more work in front of them. But their decision should sharpen Seattle’s sense of urgency. A division rival is investing in the expertise needed to get more from its players. The Mariners have to keep improving their own operation while adding enough established talent to win now.