Red Sox positional preview: Who will anchor the bullpen in 2025?
Who will step up to lead the Red Sox bullpen in 2025? Here's a closer look at the group, which was among Boston's biggest weaknesses last season.
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Red Sox positional preview: Who will anchor the bullpen in 2025? originally appeared on NBC Sports Boston
The bullpen was the Boston Red Sox’ biggest weakness in 2024. All signs point to that being the case again in 2025.
Boston lost veteran relievers Kenley Jansen and Chris Martin in free agency. The duo will be replaced by offseason addition Aroldis Chapman and fellow veteran Liam Hendriks, who’s set to return after missing all of last year recovering from Tommy John surgery.
That duo is competing for the closer role along with second-year reliever Justin Slaten, one of the club’s bright spots out of the ‘pen last season. After them, it’s anyone’s guess who will be stepping up in high-leverage situations for the Red Sox this year.
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Here’s a closer look at the bullpen arms who will look to turn the club’s weakness into a strength in 2025:
Aroldis Chapman, LHP
2024 stats: 3.79 ERA, 1.35 WHIP, 98 SO, 39 BB, 61.2 IP (68 games for Pittsburgh Pirates)
Age: 37
Contract status: Signed one-year, $10.75 million contract in free agency.
Outlook for 2025: Chapman’s days as a shutdown closer are behind him. The hard-throwing southpaw walks too many batters (at least 5.0 BB/9 in every season since 2020) at this stage of his career to be considered a truly trustworthy option in high-leverage situations.
That said, the Red Sox will lean heavily on him in 2025 after losing veterans Kenley Jansen and Chris Martin in free agency. While Chapman is no longer his dominant self, the seven-time All-Star showed last season with Pittsburgh he can still be effective and miss bats at a high rate.
Liam Hendriks, RHP
2024 stats: N/A
Age: 36
Contract status: Signed two-year, $10 million contract in 2024. Mutual option for 2026.
Outlook for 2025: After missing the entire 2024 season due to Tommy John recovery, Hendriks is battling Chapman and second-year reliever Justin Slaten for the closer role. His spring training numbers suggest Boston may be best suited going in a different direction to begin the new campaign.
Hendriks, a three-time All-Star, has allowed six earned runs on 12 hits over five innings (five appearances). Perhaps he’s simply shaking off the rust with only five regular-season games played since 2022, but throwing him straight into the fire to start the season seems unwise.
Justin Slaten, RHP
2024 stats: 2.93 ERA, 1.01 WHIP, 58 SO, 9 BB, 55.1 IP (44 games)
Age: 27
Contract status: Arbitration-eligible in 2027.
Outlook for 2025: Slaten, a Rule 5 Draft pick last winter, was an underrated bright spot for Boston during the 2024 season. The right-hander’s impressive strikeout-to-walk ratio suggests he may be the team’s best current option to close out games in 2025. If he struggles out of the gate, manager Alex Cora shouldn’t hesitate to hand the keys over to either Hendriks or Chapman.
Garrett Whitlock, RHP
2024 stats: 1.96 ERA, 1.15 WHIP, 17 SO, 7 BB, 18.1 IP (four starts)
Age: 28
Contract status: Signed four-year, $18.75 million contract extension in 2022. Club options for 2027 and 2028.
Outlook for 2025: Whitlock will presumably pitch exclusively out of the ‘pen following another injury-plagued campaign. The right-hander made only four starts in 2024 before suffering a season-ending elbow injury.
If Whitlock regains his 2021/2022 form, it’ll go a long way toward helping Boston’s bullpen enjoy a bounce-back season. He notched a 1.96 ERA across 46 relief appearances during his breakout 2021 rookie season.
Justin Wilson, LHP
2024 stats: 5.59 ERA, 1.46 WHIP, 51 SO, 13 BB, 46.2 IP (60 games with Cincinnati Reds)
Age: 37
Contract status: Signed one-year, $2.25 million contract in free agency.
Outlook for 2025: Wilson joined the bullpen this offseason as another experienced left-handed option, though his leash likely isn’t long. The veteran southpaw struggled mightily with the Reds last season and missed all of 2023 due to injury.
Wilson has a handful of solid MLB seasons under his belt, but he’ll have to earn a long-term spot on the roster with a strong start to 2025. If his woes continue, we could see fellow left-handers Adam Ottavino or Brennan Bernardino take his place.
Luis Guerrero, RHP
2024 stats: 0.00 ERA, 0.800 WHIP, 9 SO, 2 BB, 10 IP (nine games)
Age: 24
Contract status: Pre-arbitration.
Outlook for 2025: Guerrero impressed during his brief stint with the big-league club in 2024. Although he hasn’t looked as sharp this spring, he should still earn a spot on the Opening Day roster as a high-upside flamethrower. He’s a dark horse for the Red Sox closer role if Chapman, Hendriks, and Slaten can’t seize their opportunity.
Greg Weissert, RHP
2024 stats: 3.13 ERA, 1.34 WHIP, 58 SO, 20 BB, 63.1 IP (62 games)
Age: 30
Contract status: Arbitration-eligible in 2027.
Outlook for 2025: Like Slaten, Weissert was one of the bright spots in Boston’s bullpen last season. Acquired from the New York Yankees in the Alex Verdugo deal, Weissert didn’t allow an earned run over the final two months of the season. That trend has continued this spring with zero runs allowed over seven innings pitched (six appearances).
Weissert could start to make a name for himself in the big leagues if he duplicates his 2024 success. He’ll again play an important role for a group that is expected to be the club’s kryptonite again in 2025.
Cooper Criswell, RHP
2024 stats: 4.08 ERA, 1.35 WHIP, 73 SO, 31 BB, 99.1 IP (26 games, 18 starts)
Age: 25
Contract status: Arbitration-eligible in 2027.
Outlook for 2025: Criswell’s one-year, $1 million deal before the 2024 season was met with little fanfare, but it proved to be a shrewd move made by the Red Sox front office. Criswell was effective as a swingman, a role he is expected to reprise in 2025.
Criswell’s presence will be even more important with starters Brayan Bello, Lucas Giolito, and Kutter Crawford on the injured list to begin the year. We can expect the righty to make some spot-starts early in the season with Boston scheduled to play 20 games over the first 21 days.
Adam Ottavino, LHP
2024 stats: 4.34 ERA, 1.29 WHIP, 70 SO, 23 BB, 56 IP (60 games)
Age: 39
Contract status: Minor-league contract
Outlook for 2025: The Red Sox bolstered their bullpen depth by signing the veteran southpaw to a minor-league contract this offseason. If he makes the team, it’ll mark his second stint with the organization. He made 69 appearances with the club in 2021.
Ottavino has been a consistent, durable relief option throughout his 14-year MLB career. He’s getting up there in age, but it wouldn’t be a surprise to see him overtake Wilson as the No. 2 left-handed option in the ‘pen at some point this season.
Zack Kelly, RHP
2024 stats: 3.97 ERA, 1.25 WHIP, 61 SO, 27 BB, 56.2 IP (49 games)
Age: 30
Contract status: Arbitration-eligible in 2026.
Outlook for 2025: Kelly could be a difference-maker for the Red Sox bullpen in 2025. The righty is enjoying a strong spring training, allowing only two runs on four hits and one walk while striking out eight batters in seven innings (six games).
He has strong swing-and-miss stuff, but command has been an issue so far in his big-league career. Consistency will be the key to a Kelly breakout.
Brennan Bernardino, LHP
2024 stats: 4.06 ERA, 1.41 WHIP, 56 SO, 22 BB, 51 IP (57 games)
Age: 33
Contract status: Arbitration-eligible in 2026.
Outlook for 2025: It’ll be difficult for Bernardino to make the Opening Day roster with the bevy of left-handed relief options available. His production fell off a cliff last season after a remarkable start to the year (0.78 ERA over first 23 innings).
Bernardino has shown flashes of brilliance at the big-league level, but Wilson and Ottavino’s presence likely points to the 33-year-old starting the season in Triple-A.
Josh Winckowski, RHP
2024 stats: 4.14 ERA, 1.41 WHIP, 60 SO, 26 BB, 76 IP (40 games)
Age: 26
Contract status: Arbitration-eligible in 2026.
Outlook for 2025: Winckowski appears unlikely to make the Opening Day roster as his rocky 2024 season has been compounded by a rough spring training. The right-hander has allowed 10 earned runs on 11 hits and five walks in five innings.
Injuries could eventually force Winckowski back into the fold. For now, he’s probably the odd man out as Alex Cora assembles his bullpen for the club’s Opening Day matchup vs. the Texas Rangers on March 27.
