The Red Sox optioned Priester to Triple-A Worcester on Sunday, Christopher Smith of MassLive.com reports.
The right-hander was competing for a place in Boston's season-opening rotation, but his move to the minors leaves Sean Newcomb and Cooper Criswell in competition for that job. Priester combined for a 4.71 ERA in 11 appearances between the Red Sox and Pirates last season, and he'll likely be back up with the big club at some point in 2025.