Red Sox interested in Luis Castillo and Jack Flaherty

The Red Sox remain in search of a starting pitcher despite their recent blockbuster trade for Garrett Crochet.

Chief baseball officer Craig Breslow said after the trade that Boston “will continue to be aggressive in our pursuit of any avenue to improve the team,” whether that means adding a starter and/or from a right-handed hitter.

AthleticsKen Rosenthal’s Ken Rosenthal listed several weapons he says the Red Sox are involved with. The insider reiterated that the club had “inquired” about a trade for Luis Castillo from the Seattle Mariners, and said they “couldn’t be ruled out for” free agent Jack Flaherty.

Boston has long been linked to several Mariners starters in potential trade scenarios, dating back to September 13 when Rosenthal floated the idea that the Red Sox could trade first baseman Triston Casas to Seattle in exchange for pitching . The idea turned into legitimate reporting, notably by Rosenthal, this winter.

Last weekend, The Boston GlobeAlex Speier of Alex Speier reported that a trade with Casas isn’t just a random thought. Speier said Boston was “open” to selling arms to Casas, but did not explicitly mention the Mariners in his article.

“An American League executive said the Sox offered Casas as the lead in negotiations for one of that team’s branches, excluding Wilyer Abreu and the group of elite prospects ( Roman Anthony, Kristian Campbell, Marcelo Mayer) of the proposal,” Speier said. .

Whether or not Casas remains in Boston in 2025, it’s clear the organization isn’t giving up on refining its rotation. Castillo appears to remain a real trade option for them as an established and durable arm. The 32-year-old right-hander owns a 3.56 career ERA, posting a 3.64 ERA in 2024 with 175 strikeouts in 175 ⅓ innings.

Castillo has only started fewer than 25 games twice in his career: his rookie season in 2017 and the COVID-shortened 2020 season. He has only owned an ERA above 4.00 once (2018), and his opponents have owned a batting average above .250 once during his MLB career (.255 in 2021).

If the Red Sox actually want to strengthen their rotation, adding Castillo would do just that.

As for Flaherty, Rosenthal also noted that the Red Sox were interested in signing him when he was a free agent last winter. Flaherty ended up signing a one-year deal with the Detroit Tigers. He was traded to the Los Angeles Dodgers at last season’s trade deadline.

The 29-year-old right-hander hasn’t reached the level he did in 2019 when he finished fourth in National League Cy Young Award voting. That said, Flaherty had one of the best seasons of his career in 2024. He owned a 3.17 ERA over 28 starts and struck out nearly 200 batters (194). Flaherty also had 10.8 strikeouts per nine innings and held his home runs allowed per nine to 1.3.

With the absence of high-profile free agents such as Blake Snell and Max Fried, Flaherty’s stock is likely to rise as the rest of the league looks for weapons. Boston is reportedly hesitant to sign Corbin Burnes, so an arm like Flaherty might make more sense for the club if they don’t want to hand out larger contracts.