The Red Sox appear to still be in the pitching market even after trading for Garrett Crochet in exchange for four prospects, including Boston’s last two first-round picks in Kyle Teel and Braden Montgomery.

Reports have suggested that the Red Sox have called the Seattle Mariners about trading for three-time All-Star starting pitcher Luis Castillo. And The Boston Globe’s Alex Speier provided new details about Boston’s pursuit of Castillo on Friday, stating the Red Sox had “advanced conversations” with the Mariners about Castillo at this week’s MLB Winter Meetings

“According to sources, the discussions moved forward enough that the Mariners contacted Castillo’s agent to ask if the pitcher would be willing to waive his no-trade protection (something he has through the 2025 season as part of a five-year, $108 million deal that has three remaining seasons at roughly $72 million, as well as player and team options for 2028),” Speier wrote. “It is not known whether Castillo would waive the no-trade clause, or if his agent was asked about waiving it for any other teams.”

Despite coming off a down year by his lofty standards, Castillo would form quite the one-two punch atop Boston’s rotation with Crochet. The 32-year-old right-hander went 11-12 last season with a 3.64 ERA and 1.169 WHIP to go along with 175 strikeouts in 175 1/3 innings.

The difference in trading for Castillo than Crochet is the Mariners are looking for current big leaguers over a plethora of prospects, per Speier. Obtaining Castillo, who made at least 30 starts in five of his eight MLB seasons, could be a win-win for both the Red Sox and Mariners. Boston would get another top-tier starting pitcher while the Mariners would get Castillo’s big salary off their books, opening up the door to put that money toward a proven slugger.

Even with the Red Sox and Mariners looking like good trade partners, Speier reported that “talks with the Mariners about Castillo cooled” for Boston after acquiring Crochet.

But that doesn’t necessarily mean the Red Sox have stopped all communication. Speier noted the Red Sox “are likely to remain engaged” on Castillo as they pursue other avenues.

But free agent dominos, like where potential Red Sox target Corbin Burnes signs, might need to fall first before the Mariners pull the trigger on trading Castillo.