Red Sox roster decisions with prospects coming; reliever suffered stress fracture

Outfield prospect Allan Castro’s offensive upside has always excited the Red Sox, but he has struggled since he made the jump from High-A to Double-A in 2024.

Castro, 23, has a .330 on-base percentage, .380 slugging percentage and .710 OPS across 1,010 plate appearances between Double-A and Triple-A.

But he finished the 2026 season with an excellent September at Triple-A Worcester, his final month before being eligible for minor league free agency this offseason. He batted .300 with a .371 on-base percentage, .650 slugging percentage and 1.021 OPS in 70 plate appearances.

He crushed six home runs in the final seven games of the season. Statcast tracked the distance of four of the home runs. They went 441 feet, 410 feet, 394 feet and 391 feet.

Castro — who Baseball America ranked Boston’s No. 26 prospect entering 2026 — is in great shape physically and hits from both sides of the plate. He played all three outfield positions in 2026 and showed his power potential late in the season after having not slugged much the past couple of seasons.

But his time in the organization might end if the Red Sox don’t select him to their 40-man roster before minor league free agency begins five days after the World Series ends.

Boston rarely adds players to the 40-man roster to prevent them from reaching minor league free agency, but it has happened before. Then-president of baseball operations Dave Dombrowski did it with two players (outfielder Bryce Brentz and left-handed pitcher Williams Jerez) at the beginning of the 2017-18 offseason.

Might Boston do it again with Castro this year?

He’s part of a Red Sox minor league free agent class that also includes notable pitching prospects and 40-man candidates Angel Bastardo, Yordanny Monegro and Jeremy Wu-Yelland.

“He’s definitely a consideration” to be added to the 40-man roster, according to a source, but the Red Sox need to work through the rest of their outfield depth and gain more clarity about if the Rule 5 Draft will happen this offseason.

The Rule 5 Draft takes place annually at the Winter Meetings in December, but the owners are expected to lock out the players on Dec. 1 when the current collective bargaining agreement expires.

The major league portion of the Rule 5 Draft didn’t take place during the last lockout that lasted from Dec. 1, 2021 to March 10, 2022. The meetings were canceled and only a minor league Rule 5 Draft happened.

A Dec. 1 lockout again seems inevitable and it is likely to last longer than the work stoppage during the 2021-22 offseason, meaning maybe no draft again.

The deadline to protect Rule 5 Draft players is Nov. 17. Boston has several borderline candidates in Blake Wehunt, Mikey Romero, Brooks Brannon, Hayden Mullins, Johanfran Garcia and Braiden Ward.

With the lockout looming and borderline candidates anyway, the Red Sox could take their chances and protect nobody — or only one player with Wehunt being probably the most likely. That would give them more roster space to carry a player like Castro during an offseason when there won’t be many spots.

The Red Sox will have little roster flexibility because they have only three pending free agents coming off the 40-man roster. Only two players — Isiah Kiner-Falefa and Patrick Sandoval — will become free agents the day after the World Series ends. Sonny Gray also is expected to opt out of his contract to become a free agent within a five-day window following the conclusion of the World Series.

Therefore, only three 40-man roster spots will open. But then the Red Sox have seven players on the 60-day injured list — Kutter Crawford, Zack Kelly, Johan Oviedo, Eduardo Rivera, Justin Slaten, Triston Casas and Eli White — who they must transfer back to the 40-man roster. That also must be done by the fifth day after the World Series ends, the same day minor league free agency begins.

That means the Red Sox will need to cut at least four players and five players if they were to add Castro.

Boston always could re-sign Castro in minor league free agency, although that’s not a certainty. Castro could leave for a better opportunity somewhere else. And if the Red Sox were to re-sign him to a minor league deal, he would become Rule 5 Draft eligible.

Castro profiles as a potential fourth outfielder who is better from the left side of the plate. That said, two of his six home runs in September were vs. lefties. He pulled one home run to left field and another to left-center field.

Kelly suffered a stress fracture

Red Sox right-handed reliever Zack Kelly recorded a 3.31 ERA in 17 outings before Boston optioned him to Worcester on May 22. He pitched for Worcester until suffering an arm injury in early July. He did not pitch again during the 2026 season. Boston recalled him to place him on the 60-day IL with right elbow inflammation on July 21.

Kelly ended up later being diagnosed with an olecranon stress fracture. He’s aiming to start throwing again in two to three weeks.

Anderson batting .344 in AFL

Red Sox first base/third base prospect Antonio Anderson is 11-for-32 (.344) with a .500 on-base percentage, .688 slugging percentage and 1.188 OPS in nine games in the Arizona Fall League. He has two home runs, three doubles, one triple, 10 RBIs, eight runs, 10 walks and 13 strikeouts.

He hit a ninth-inning go-ahead grand slam for the Solar Sox on Oct. 9. It went 403 feet with a 115.2 mph exit velocity.

The Red Sox drafted Anderson, 21, in the third round in 2023 and signed him to a $1.5 million bonus, well above his slot value of $846,000.

He struggled in his first few years of pro ball but had a breakout season in 2026.

Other minor league free agents

As noted above, Bastardo, Monegro and Wu-Yelland are all part of Boston’s 2026 minor league free agent class and can declare five days after the World Series ends.

Boston lost Bastardo, 24, to the Blue Jays in the 2024 Rule 5 Draft but Toronto returned him to the Red Sox in April. He had spent 2025 injured. He posted a 4.64 ERA in 40 relief appearances for Worcester but held opponents to just a .212 batting average. He had issues with command, walking 33 batters in 54 ⅓ innings.

Monegro — who underwent Tommy John surgery — spent the first five months of 2026 rehabbing. The 24-year-old righty returned in late August and made three starts down the stretch. Baseball America ranks him Boston’s No. 25 overall prospect.

Wu-Yelland, Boston’s fourth-round pick in 2020, struggled with a 7.31 ERA and 29 walks in 32 innings for Portland in 2026.

All are candidates along with Castro. Of course Bastardo was thought of highly enough last offseason to be taken in the Rule 5 Draft.

Guerrero under control for three more years

The Red Sox still have three more years of team control over 35-year-old Tyron Guerrero, whom they signed to a minor league contract last offseason.

MLBTradeRumors.com projects he will make $1.1 million in salary arbitration for 2027.

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