Even after Boston swung a blockbuster trade for new ace Garrett Crochet, several reports indicated the Red Sox had their sights set on Castillo. Seattle boasts very appealing starting pitching depth, and Boston has the assets it would take to pry one of those arms out of the Pacific Northwest.

Castillo appears to be the likeliest candidate given his age (32) and the term on his current contract. The Boston Globe’s Alex Speier on Friday provided an update on the Red Sox’s interest in the three-time All-Star, and in doing so, the team insider included a note on Casas.

“While there’s been speculation about a trade that would send Castillo to Boston and first baseman Triston Casas to Seattle, sources said Casas hadn’t been involved in the conversations,” Speier wrote. “Instead, the Mariners were targeting pitching (since they’d have a vacancy if dealing Castillo) and other infield positions.”

It would be pretty reckless for the Red Sox to include Casas in a trade for Castillo, even though the latter could be under contract through the 2028 season. The first baseman isn’t even arbitration-eligible until 2026, and he’s shown flashes of All-Star potential.

Not to mention, there would be inherent risks to a Castillo trade no matter what the Boston return would look like.