The Boston Red Sox bullpen was among MLB’s best in 2025. It’s a similar group heading into 2026, though there is one glaring weakness that must be addressed.
Other than All-Star closer Aroldis Chapman, the Red Sox don’t have any reliable left-handed relief pitchers on their current roster. Jovani Moran is the only other southpaw reliever with MLB experience, and he has made only two big-league appearances in the last two seasons.
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Boston parted ways with left-handers Brennan Bernardino, Steven Matz, and Justin Wilson during the offseason. Fortunately, there are still a handful of solid LHP options available in free agency, including Jalen Beeks and Danny Coulombe. Chief baseball officer Craig Breslow & Co. are reportedly still looking to add a left-handed bullpen arm to the mix.
For now, it’s a right-hander-heavy group with elite arms in the back end and some question marks in the middle. Here’s a closer look at the projected bullpen for 2026:
Aroldis Chapman, LHP
2025 stats: 1.17 ERA, 0.701 WHIP, 85 SO, 15 BB, 32 saves, 61.1 IP (67 appearances)
Mark J. Rebilas-Imagn Images
Mark J. Rebilas-Imagn Images Aroldis Chapman had the best season of his 16-year career after joining the Red Sox last offseason.
Chapman blew away everyone’s expectations and was far and away the best reliever in baseball in 2025. The “Cuban Missile” put up the best numbers of his career, and at one point in the season, he set a streak of 50 straight batters faced without a hit allowed. He was virtually untouchable for nearly the entire campaign.
It’s hard to believe Chapman can duplicate his historic 2025 performance, but the Red Sox will be thrilled to get anything even remotely close to that production from the 37-year-old this upcoming season. Although regression is likely, the back end of Boston’s bullpen remains in good hands.
Garrett Whitlock, RHP
2025 stats: 2.25 ERA, 1.083 WHIP, 91 SO, 24 BB, 72 IP (62 appearances)
Mark J. Rebilas-Imagn Images
Mark J. Rebilas-Imagn Images Garrett Whitlock was lights out last season in his return from elbow surgery.
Whitlock was lights-out last season in his return to the Red Sox bullpen. After missing most of 2024 due to injury, he was Boston’s most reliable reliever outside of Chapman. The 29-year-old could be counted on to consistently pitch clean innings to set up Chapman for saves.
When Whitlock ran into trouble in 2025, it was often because he was asked to pitch more than one inning. The Red Sox leaned on him a bit too heavily at times, though when he’s as dominant as he often is, it’s easy to understand why.
Whitlock has established himself as one of the best relievers in MLB. The days of Boston trying to utilize him as a starting pitcher should be over.
Justin Slaten, RHP
2025 stats: 4.24 ERA, 1.088 WHIP, 25 SO, 10 BB, 34 IP (36 appearances)
Patrick Gorski-Imagn Images
Patrick Gorski-Imagn Images Justin Slaten missed three months of the 2025 season due to a nerve issue in his neck.
Many expected Slaten to begin the 2025 season as the Red Sox’ closer, even after the club signed Chapman. The 28-year-old was outstanding in 2024, posting a 2.93 ERA and 1.012 WHIP in 44 appearances.
Instead, the Red Sox rolled with Chapman, and Slaten was solid in the first few months of the season before going down with an injury in late May. He returned at the end of August and struggled for the rest of the campaign.
If Slaten returns to 2024 form, he’ll be a major difference-maker for this Boston bullpen.
Greg Weissert, RHP
2025 stats: 2.82 ERA, 1.164 WHIP, 57 SO, 21 BB, 67 IP (72 appearances)
David Butler II-Imagn Images
David Butler II-Imagn Images Greg Weissert stepped up to help stabilize the Red Sox bullpen in 2025.
Weissert played an important role in the Red Sox bullpen last year. He had his fair share of ups and downs, but when the dust settled on the 2025 season, he ended up with some solid numbers with the most appearances of any Boston reliever.
The 31-year-old is best suited for a middle relief role rather than high-leverage situations, as he tied for the second-most blown saves (nine) in MLB last season. That said, Weissert came up big on several occasions when called upon, and he should have a key role again in 2026.
Jovani Moran, LHP
2025 stats: 6.75 ERA, 2.000 WHIP, 5 SO, 3 BB, 4 IP (two appearances)
Troy Taormina-Imagn Images
Troy Taormina-Imagn Images Other than Aroldis Chapman, Jovani Moran is the only left-handed reliever with MLB experience on Boston’s roster.
There’s pressure on Moran heading into 2026 as Boston’s only left-handed reliever other than veteran closer Aroldis Chapman. The 28-year-old has only made two MLB appearances over the last two years due to Tommy John surgery that forced him to miss all of 2024 and most of 2025.
Moran’s best season came with the Minnesota Twins in 2023, when he posted a 2.21 ERA and 1.057 WHIP with 54 strikeouts and 18 walks in 31 appearances. He rekindled that success this offseason in the Puerto Rican Winter League, amassing an 0.82 ERA with a 0.818 WHIP in 11 appearances.
If the Red Sox get the 2023 version of Moran, they’ll be in great shape. But since that’s far from a guarantee, Boston should add an experienced left-handed reliever to the roster before Opening Day.
Zack Kelly, RHP
2025 stats: 4.58 ERA, 1.33 WHIP, 35 SO, 12 BB, 35.1 IP (28 appearances)
Brad Penner-Imagn Images
Brad Penner-Imagn Images Zack Kelly hopes to bounce back from a lackluster season that was marred by injuries.
Kelly hopes to be more effective than he was in 2025, when he struggled with inconsistency and dealt with a midseason oblique sprain. He has shown flashes of brilliance in his four seasons with the club, but he could quickly end up back in Triple-A Worcester if his inconsistency remains an issue in 2026.
Ryan Watson, RHP
2025 stats: 4.26 ERA, 1.461 WHIP, 64 SO, 16 BB, 50.2 IP (46 appearances in Triple-A)
Maddie Malhotra/Boston Red Sox/Getty Images
Maddie Malhotra/Boston Red Sox/Getty Images Newcomers Ryan Watson (right) and Tyler Samaniego (left) hope to earn spots in Boston’s bullpen for 2026.
Watson arrived in Boston via an offseason trade with the Athletics, who selected him in the Rule 5 draft. The 28-year-old has yet to make his MLB debut but offers some intriguing upside with his elite extension and effective pitch mix.
As a Rule 5 pick, Watson must be on the Red Sox’ 26-man roster for at least 90 days. If he’s removed from the active roster, he must be placed on outright waivers. He cannot be optioned to the minors.
The Red Sox have done well with Rule 5 players in recent years. Whitlock and Slaten both arrived as Rule 5 selections.
Tyler Samaniego, LHP
2025 stats: 3.99 ERA, 1.043 WHIP, 44 SO, 11 BB, 38.1 IP (30 appearances across rookie ball, Low-A, High-A, and Double-A)
The Red Sox acquired Samaniego as part of the Johan Oviedo trade with the Pittsburgh Pirates. Samaniego, 27, had spent all five of his professional seasons in the Pirates organization, though he never reached the majors with Pittsburgh. With a shortage of left-handed relievers on the roster, the Red Sox may have to lean on Samaniego at times this upcoming season.
Samaniego has a mid-90s fastball that tops out at 97 mph, a solid sinker, and an average slider. He took a noticeable step forward with his command in 2025, which bodes well for his odds of breaking out for Boston in 2026.
Other options
- LHP Patrick Sandoval is a candidate for a bullpen role if he doesn’t earn a spot in the starting rotation. The former Los Angeles Angels starter is still working his way back from Tommy John surgery.
- RHP Kutter Crawford will likely earn a spot in the bullpen if all goes well in his return from injury. Crawford has had success as a starter with Boston, but he’s best suited for a relief role in 2026.
- Top left-handed pitching prospects Payton Tolle and Connelly Early could begin the season in the bullpen if they make the Opening Day roster. Early is a strong candidate for the No. 5 starter role.
