With the World Series set to begin on Friday and the offseason rapidly approaching, the Boston Red Sox face several key decisions. Both Sonny Gray and Garrett Whitlock have options they can exercise or decline, with Gray's being mutual.  With seven players set to return to the 40-man roster when the injured list expires five days after the World Series, Boston will have to trim at least four players. The Red Sox 40-man roster crunch gets even tougher when you factor in minor league free agents. Of the 19 minor leaguers set to become free agents after the World Series, Boston could add three to the 40-man roster to keep them in the organization. 

Here’s what you you need to know: 

Boston’s No. 36-rated prospect, according to SoxProspects.com, the 22-year-old Castro signed with the Red Sox for $100,000 out of the Dominican Republic in the 2019 international free agent class. 

The switch-hitting outfielder spent the 2026 season with Triple-A Worcester, where he hit .252/.325/.397/.722 with 15 home runs, 18 doubles and 20 stolen bases, driving in 77 runs. 

While he doesn’t excel at any one thing, Castro does a lot of things well, ranking in the 50th percentile or higher in average exit velocity (88.3 mph, 55th percentile), strikeout rate (18.1 percent, 75th percentile), chase rate (27.5 percent, 51st percentile), whiff rate (22.4 percent, 71st percentile), and zone contact rate (86.7 percent, 73rd percentile). 

Defensively, Castro profiles as a corner outfielder; however, he can also play center field. 

As for whether the team would consider adding Castro to the 40-man roster to avoid losing him in free agency, MassLive.com’s Christopher Smith reports that he is “definitely a consideration.” However, adding Castro to the 40-man roster would further complicate both the team’s roster crunch and crowded outfield picture. 

Once one of the highest-rated arms in the Red Sox system, Monegro spent much of the 2026 season recovering from Tommy John surgery undergone in August 2025. 

The 24-year-old right-hander briefly returned before the minor league season ended, making two appearances with High-A Greenville and one with Double-A Portland. In those three starts, Monegro allowed three earned runs on five hits, striking out eight and walking six. 

Monegro joined the Red Sox organization as part of the 2020 international free agent class, signing for $35,000. In six minor league seasons, Monegro has posted a 3.24 ERA over 66 career appearances, striking out 11.24 batters per nine innings, walking 3.93 per nine innings, allowing a .221 batting average against. 

He is currently ranked as the No. 24 prospect in the Red Sox system per SoxProspects. 

Originally an international free agent signee in the 2018 class, the 24-year-old right-handed reliever spent the 2026 season with Triple-A Worcester. In 40 appearances, Bastardo posted a 4.64 ERA. 

Bastardo has massive swing-and-miss stuff, including a 36 percent whiff rate (90th percentile) and a 30.8 percent chase rate, for a 31.9 percent strikeout rate. However, he struggled mightily with command, walking 14.4 percent of batters faced. 

The Toronto Blue Jays selected Bastardo in the 2024 Rule 5 Draft. After spending the entire 2025 season rehabbing in the Toronto system, he failed to make the team out of spring training and was returned to the Red Sox. 

The 24-year-old is currently ranked as the No. 18 prospect in the Red Sox organization. 

Of course, the team could let the trio hit the open market, hoping to re-sign them to minor league deals. However, they would then become eligible for selection in the Rule 5 Draft  

Among the rest of the Red Sox pending minor league free agents that don’t figure to be added to the 40-man roster: 

Catchers: Tomas Nido, Jason Delay, Ronald Rosario

Infielders: Vinny Capra

Pitchers: John Brebbia, Patrick Halligan, Seth Martinez, Sam McWilliams, Osvaldo Berrios, Patrick Halligan, Hobie Harris, Kyle Keller, Erik Rivera, Michael Sansone, Reidis Sena, Devin Sweet and Jeremy Wu-Yelland 

The Red Sox will have until five days after the World Series to add any pending minor league free agent to the 40-man roster.