The Boston Red Sox bullpen rebuild is officially underway, and for good reason.

The Red Sox led the entire American League with 31 blown saves in 2024. The Chicago White Sox and Miami Marlins were the only teams with lower save percentages, finishing with 41 and 62 wins, respectively.

Considering Boston finished 81-81, just five games out of the final AL Wild Card spot, it’s no exaggeration to say that the Red Sox’ lackluster bullpen stood between them and a playoff spot .

Closer Kenley Jansen and setup man Chris Martin both left in free agency at the end of the year, costing the Red Sox their two most experienced late-inning options. The 37- and 38-year-old right-handers combined for a 3.36 ERA and 1.5 WAR in 99.0 innings in 2024, compared to a 2.25 ERA and 4.0 WAR over 96.0 innings in 2024 2023.

The Red Sox made a big move to replace that dwindling production by signing Aroldis Chapman to a one-year, $10.75 million contract on Tuesday morning. Chapman was the second reliever the Red Sox signed this offseason, as the team signed 37-year-old left-hander Justin Wilson to a one-year contract in November.

With these two veterans on the team, Boston has a much clearer picture of what its bullpen could look like in 2025.

Chapman, a seven-time All-Star, has not been a full-time closer since 2021. Since 2022, he has finished an average of 18 games per season after finishing an average of 49 games in the non-COVID seasons between 2012 and 2021.

The soon-to-be 37-year-old southpaw will likely remain a reliever for the Red Sox, who will see Liam Hendriks return from Tommy John surgery.

Hendriks made three consecutive All-Star appearances with the Ahtletics and White Sox from 2019 to 2022 and even received Cy Young votes in 2020 and 2021. During that time, the right-hander posted a 2.26 ERA, 0.883 WHIP and 13.5 strikeouts per nine innings and a 9.4 WAR, converting in 114 of his 132 save opportunities.

While Hendriks was limited to five appearances in 2023 and zero appearances in 2024 due to cancer and elbow surgery, he is still in position to be Boston’s closer heading into his age-36 season.

Then there’s Justin Slaten, a 26-year-old who went 6-2 as a rookie in 2024 with a 2.93 ERA, a 1.012 WHIP, 9.4 strikeouts per nine innings and a 0.9 WAR game came. He came from the New York Yankees Rule 5 draft last year and is now a solid seventh-inning option for the foreseeable future.

Greg Weissert, who the Red Sox also got from the Yankees in the Alex Verdugo trade last December, went 4-2 with a 3.13 ERA and 0.6 WAR in 2024. Left-hander Brennan Bernardino and right-hander Josh Winckowski both had ERAs over 4.00 in 2024, but that was after they posted 3.20 and 2.88 ERAs in 2023.

Swingmen Kutter Crawford and Cooper Criswell could also join the Red Sox bullpen. Lucas Giolito is expected to return from an internal brace, joining Brayan Bello and Tanner Houck. If the team relies on rookie Richard Fitts to open 2025 in the big leagues, or if it adds multiple starters via free agency or a trade, Crawford and Criswell will become long-term backups.

Garrett Whitlock could be in a similar situation when he returns from his own internal brace given his years of injury issues. The 28-year-old right-hander is 18-11 with a 3.39 ERA, a 1.146 WHIP and a 5.8 WAR in his career, but he has yet to surpass 80 innings in a single season.

Michael Fulmer was an All-Star and Rookie of the Year winner as a starter in the mid-2010s, but that was before his own injuries derailed his career. While he eventually became a solid backup player for the Detroit Tigers, Minnesota Twins and Chicago Cubs, Fulmer underwent UCL surgery and signed a minor league contract with Boston last winter.

With all that said, here’s how the Red Sox bullpen is shaping up to open in 2025:

CL: Liam Hendriks (R)
SU: Aroldis Chapman (left)
SU: Justin Slaten (R)
MR: Justin Wilson (left)
MR: Greg Weissert (R)
MR: Brennan Bernardino (left)
LR: Cutter Crawford (R)
LR: Cooper Criswell (R)

Assembling this eight-man group would mean Winckowski forfeiting his third and final minor league option. It’s also expected that Whitlock will begin the year on the injured list, that Giolito will be cleared for Opening Day and that two starters – or one and Fitts – will be brought in to round out the rotation.

Bernardino could be an option in place of Winckowski, but another lefty in the mix could prove crucial. And while Criswell still has an option, Boston may need another innings-muncher if both a rusty Giolito and a rookie Fitts are installed as starters.

Zack Kelly, Cam Booser, Luis Guerrero and Zach Penrod, all of whom still have multiple options, would start in Triple-A in this scenario. Considering they each held their own in the big leagues last season, they will provide Boston with respectable injury insurance in 2025.

Fulmer would also open the year in the minors since his contract calls for it anyway.

There are still a lot of questions in Boston’s bullpen, like what they plan to do when Whitlock returns or whether Crawford himself could become a trade chip. Still, the Red Sox have options and reason for hope when it comes to their 2025 roster full of replacements.

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