Boston Red Sox Roster: Way Too Early Look at 2027 Bullpen

Headed by All-Star closer Aroldis Chapman and Garrett Whitlock, the Boston Red Sox bullpen posted a 3.00 ERA in 2026, the best mark in baseball. With Whitlock's option picked up for 2027, the Red Sox are expected to return most of their bullpen next season. 

Here's a way too early look at the 2027 Red Sox bullpen. 

No surprises here, as manager Chad Tracy has one of the best 1-2 punches in baseball in a pair of All-MLB reliever nominees. In 51.2 innings, Chapman posted a 1.92 ERA, the 10th-lowest mark among all qualified relievers, while his 35 saves were the fifth-most in baseball. It was a historic 17th big-league season for the 38-year-old flamethrower, as he became the all-time reliever strikeout king, surpassing Hall of Famer Hoyt Wilhelm. Chapman also rose to ninth on the all-time saves leaderboard, passing former Minnesota Twins closer Joe Nathan and former Red Sox pitcher and Hall of Famer Dennis Eckersley with 402 career saves. After surpassing 40 innings pitched and passing his end-of-season physical, Chapman vested his option for 2027, which will pay him $13 million. 

Whitlock made 54 regular-season appearances, setting things up for Chapman, posting a 1.72 ERA, the sixth-lowest mark among 143 qualified relievers. In addition to the impressive ERA, Whitlock ranked 12th among all relievers in win probability added with 2.73.  

In 104 innings, the duo allowed only 21 earned runs, for a 1.82 ERA. Barring the unforeseen, the pair will be back in 2027, once again as one of the sport's best bullpen duos. 

A true diamond-in-the-rough find for the Red Sox pitching department, the 35-year-old Guerrero was one of baseball's best relievers for much of the 2026 season after not appearing in a major league game since 2019. In 40.2 innings, Guerrero posted a 3.10 ERA, but the most impressive part of his career renaissance was his ability to control the strike zone. After walking 5.7 batters per nine innings in his first 106 innings in the big leagues, the 35-year-old right-hander walked only 1.77 per nine innings, the 12th-lowest among relievers with at least 40 innings of work in 2026. 

It was an up-and-down year for Slaten as he battled injuries for much of the season. The 30-year-old right-hander was limited to just 31.1 innings of work across 36 outings, where he posted a 4.60 ERA. However, a fielding independent pitching (FIP) of 3.04 suggests he was the victim of some bad luck. Slaten's season came to an early end when he received a PRP injection in his right elbow to treat degenerative changes in his flexor mass. Assuming he returns to full health in 2027, Slaten is expected to remain a key piece of the bullpen picture, helping bridge the gap to Chapman. 

Acquired from the San Francisco Giants at the trade deadline in exchange for former top prospect Marcelo Mayer, Miller got off to a great start to his Red Sox career, making 10 straight scoreless appearances. However, the 28-year-old left-hander's regular season ended in disaster as he allowed six earned runs in his final 4.1 innings. Those end-of-season struggles continued into the postseason, where Miller made only two appearances in the Wild Card series against the New York Yankees, allowing a solo home run to first baseman Ben Rice in the Game 1 loss and an RBI single to left fielder Cody Bellinger in the season-ending Game 2 loss. Despite the poor end to his season, Boston paid a high price to acquire him, and with limited dependable left-handed options besides Chapman, Miller will be a major player in the 2027 bullpen. 

Houck, Crawford and Oviedo represent relative unknowns in the Red Sox pitching picture. Houck briefly returned from 2025 Tommy John surgery to make a start in the final regular-season game. Crawford has missed each of the last two seasons with a litany of injuries, but appeared to be nearing a return at the end of the regular season when his scheduled rehab start was canceled due to rain and not made up. Oviedo, acquired in an offseason deal with the Pittsburgh Pirates, made only one appearance in 2026 before landing on the injured list with an elbow strain that ended his season. All three could find themselves in the mix for the fifth starter spot in the rotation, depending on how the offseason shakes out, but could also serve as rotation depth in Triple-A or a long-relief option in the bullpen. 

Bello also represents a relative unknown in Boston's pitching plans. After struggling as a starter, the 27-year-old right-hander moved to a bulk relief role, posting a 1.98 ERA in 63.2 innings. However, Bello got a pair of starts at the end of the season and succeeded, allowing only one earned run on nine hits, striking out 13 and walking only two. Entering the fourth year of the six-year, $55-million contract signed in 2024, the organization will certainly want Bello to reclaim his spot in the rotation. However, he should be a solid long relief option if he loses the battle for the fifth starter spot.  

Such is the life of a middle reliever; both Weissert and Moran saw the highs and lows of the role in 2026. After posting a 2.52 ERA in his first 36 appearances of the season, Moran showed signs of wear down the stretch. In his final 14 regular-season appearances, the 29-year-old left-hander allowed nine earned runs in 15.1 innings before missing the postseason roster. 

In his first 48 appearances of the season, Weissert posted a 3.97 ERA in 45.1 innings pitched. The 31-year-old right-hander struggled in particular when taking over in situations with men already on base, allowing 13 of 29 inherited runners to score, which, at the time, was the third-most among all relievers. After a brief demotion to Triple-A to get a fresh arm in a taxed bullpen, Weissert returned to the big leagues and turned the tide on his season. In his final 15 regular-season appearances, Weissert allowed only two earned runs on 13 hits. Perhaps most importantly, Weissert allowed only two of nine inherited runners to score. 

Gamboa and Olds were both late-season additions to the Red Sox bullpen as it dealt with injuries to Whitlock, Guerrero, and Slaten. In 14 regular-season appearances, the 26-year-old Olds allowed only two earned runs in 15.2 innings, striking out 20 and walking eight. After spending the 2025 season in the Korean Baseball Organization, Gamboa signed a minor league contract with the Red Sox for 2026. In an up-and-down relief role, Gamboa made 21 appearances in Boston, allowing seven earned runs over 33 innings, mostly in mop-up duty. With two seasons of minor league options remaining, Gamboa will likely be back in the mix in a similar role as the one he held in 2026.