Breaking Down Boston Red Sox's Bullpen After Addition of All-Star Aroldis Chapman

Aroldis Chapman joined the Boston Red Sox on a one-year, $10.75 million contract on Tuesday, slotting him into a bullpen that already featured Liam Hendriks, Justin Slaten and Justin Wilson.

Aug 23, 2024; Pittsburgh, Pennsylvania, USA; Pittsburgh Pirates relief pitcher Aroldis Chapman (45) reacts after striking out Cincinnati Reds center fielder Stuart Fairchild (not pictured) to end the eighth inning at PNC Park. Pittsburgh won 6-5. / Charles LeClaire-Imagn Images

The reconstruction of the Boston Red Sox's bullpen 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, and they finished with 41 and 62 wins, respectively.

Considering Boston finished 81-81, just five games out of the final AL Wild Card spot, it isn't a stretch to say that the Red Sox's lackluster bullpen stood between them and a playoff berth.

Closer Kenley Jansen and setup man Chris Martin both hit 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 pitched in 2024, compared to their 2.25 ERA and 4.0 WAR across 96.0 innings in 2023.

The Red Sox took a major step in replacing that fading production by signing Aroldis Chapman to a one-year, $10.75 million contract Tuesday morning. Chapman was the second reliever the Red Sox added this offseason, as the team signed 37-year-old left-hander Justin Wilson to a one-year deal in November.

With those two veterans in the fold, Boston has a much clearer picture of what its bullpen may look like come 2025.

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

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

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

While cancer and elbow surgery limited Hendriks to five appearances in 2023 and zero in 2024, he is still in line to serve as Boston's closer in his age 36 season.

Then there's Justin Slaten, a 26-year-old who went 6-2 with a 2.93 ERA, 1.012 WHIP, 9.4 strikeouts per nine innings and a 0.9 WAR as a rookie in 2024. He came over from the New York Yankees in last year's Rule 5 Draft 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 join the Red Sox's bullpen as well. Lucas Giolito is set to return from an internal brace procedure, joining Brayan Bello and Tanner Houck in the rotation. If the team trusts rookie Richard Fitts to open 2025 in the big leagues, or if they add multiple starters via free agency or trade, then Crawford and Criswell will become long relievers.

Garrett Whitlock could be in a similar boat once he returns from his own internal brace procedure, considering his injury issues over the years. The 28-year-old righty is 18-11 with a 3.39 ERA, 1.146 WHIP and 5.8 WAR for his career, but he has yet to surpass 80 innings in a single season.

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

With all of that being said, here is how the Red Sox's bullpen is shaping up to open 2025:

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

Putting together that eight-man group would involve burning Winckowski's third and final minor league option. It also assumes Whitlock starts the year on the injured list, that Giolito is cleared for Opening Day and that two starters – or one and Fitts – are brought in to round out the rotation.

Bernardino could get optioned in place of Winckowski, but having another lefty in the mix could prove vital. And while Criswell also has an option left, Boston may need another innings-eater if a rusty Giolito or rookie Fitts are both being leaned on as starters.

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

Fulmer would also open the year in the minors, since that is what his contract calls for anyways.

There are plenty of questions left in Boston's bullpen, such as what they plan to do when Whitlock returns or if Crawford could become a trade chip in his own right. Still, the Red Sox have options and reason for hope when it comes to their cupboard full of relievers entering 2025.

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