Relievers:
Matt Barnes: under control through 2021 (arbitration)
Brandon Workman: under control through 2020 (arbitration)
Heath Hembree: under control through 2021 (arbitration)
Darwinzon Hernandez: under control through 2024 (team control)
Josh Taylor: under control through 2024 (team control)
Marcus Walden: under control through 2024 (team control)
Colten Brewer: under control through 2024 (team control)
Travis Lakins: under control through 2024 (team control)
Brian Johnson: under control through 2023 (team control)
Hector Velazquez: under control through 2023 (team control)
Andrew Cashner: free agent after season (did not reach vesting option)
Coming into the season, the bullpen was the main source of concern for fans, but they ended up performing pretty well, ranking 9th in FIP and 12th in xFIP.
The entire bullpen is intact for next season, with only Cashner hitting free agency. It is a group with plenty of depth and should be a strength next year. They could use a real closer with experience closing but it is unclear if they are willing to spend to get that.
The Red Sox have said they want to get under the $208 million luxury tax threshold, so it will be interesting to see if they go after a big name reliever in free agency.