The Boston Red Sox continue to target upgrades to their starting rotation as the 2024-2025 offseason goes on. One name that has surfaced repeatedly in the team’s quest is Seattle Mariners righty and three-time All Star Luis Castillo.

With his solid 3.56 career ERA and ability to handle workloads of more than 160 innings pitched — a goal he has reached five times in his eight-year career — Castillo appears to be an ideal candidate for a rotation that will already have dominant lefty Garrett Crochet as its ace and anchor.

But what would it take for the Red Sox to land Castillo, who will enter the third year of a five-year $108 million contract in 2025 — and would the price be worth it?

Casas Not Enough on His Own to Land Castillo

The name of Triston Casas has been repeatedly reported to come up in talks between the Mariners and Red Sox concerning a Castillo trade. While multiple media sources on the Red Sox beat have attempted to debunk those rumors, the reporting that Casas was not, in fact, involved in the discussions, does not seem to have quelled speculation on the Mariners’ side.

According to one Mariners’ insider journalist, Seattle would not only demand the 24-year-old, lefty-swinging first baseman from the Red Sox in exchange for Castillo, but Boston would need to throw in a “sweetener.” Presumably, that means Casas plus one of the Red Sox’ valuable minor league prospects.

“They want Major League talent. And they would want a guy that can bat in the middle of the order or the top five spots in the order,” said Ryan Divish, who covers the Mariners for The Seattle Times, in an appearance on the Baseball Isn’t Boring podcast. “If the Red Sox were interested in Casas for Castillo, the Mariners would probably want a sweetener in it. Somebody else who could help them at the MLB level. That would maybe get done.”

A “sweetener” who could quickly contribute to the Major League Seattle team appears to narrow down the choices to the Red Sox top set of prospects, and the team already traded one of those when it sent catcher and 2023 first-round draft pick Kyle Teel to the Chicago White Sox in the deal for Crochet.

Red Sox No. 22 Prospect Blaze Jordan Part of Castillo Deal?

According to Jim Bowden, former general manager for the Cincinnati Reds and Washington Nationals, Casas plus the organization’s 22nd-ranked prospect Blaze Jordan in a deal for Castillo would be a “win-win for both organizations.”

Jordan, a combination first baseman and third baseman, does not appear Major League ready. Despite being a “legendary power hitter as an amateur,” according to MLB.com, winning the High School Home Run Derby at the 2019 All-Star Game, Jordan’s power bat has proven “less dangerous” at the professional level.

Other Red Sox observers consider the idea of Casas plus a “sweetener” far too steep a price to pay.

“Casas and a sweetener for Luis Castillo would be beyond insane. And that’s from someone who loves Castillo,” wrote Play Tessie podcast host Nat Gordon on his X (formerly Twitter) account. “I feel like I’m taking crazy pills. How do people not think Triston Casas is an ultra valuable asset? Keep this guy and let him rake!!”