White Sox add Castillo as rotation depth becomes a survival question

The White Sox acquired Luis Castillo from Seattle on Sunday, sending Seranthony Domínguez, Nolan Jones, and catching prospect Boston Smith to the Mariners. It is the kind of move a contender makes when the standings are fine but the infrastructure underneath them is not.

Ten players are currently on the injured list, and the rotation has been running on Davis Martin, Anthony Kay, and Erick Fedde — a serviceable group, not a deep one. Martin has been the anchor all year at 11-5 with a 3.55 ERA, but the staff behind him has been stretched thin enough that Tyler Schweitzer's recent workload spike is worth watching. Castillo is a former All-Star who has been one of the more durable starters in the game over the past several years. He gives Chicago an arm that can eat innings without the rotation fraying further.

The cost is real. Domínguez was the team's closer, and the bullpen was already the shakier half of the pitching staff. Grant Taylor and Sean Newcomb will absorb those save situations going forward. Whether they can handle it is the short-term question the next 10 days will start to answer.

At 58-53 with 51 games left, the White Sox hold the division lead and the No. 2 seed in the AL. The margin is comfortable enough that one trade does not define the season, but the injury list is long and the offense has cooled considerably. Castillo steadies the rotation. Everything else still needs to hold.