The Rays acquired Guerrero from the Red Sox on Tuesday in exchange for Tristan Gray.
Guerrero was outrighted off Boston's 40-man roster last week after passing through waivers unclaimed, but now he's on the move to a new organization. The right-hander holds a 2.63 ERA but a 19:16 K:BB across 27.1 frames covering parts of two major-league seasons. Guerrero has a big arm and the Rays will now be tasked with getting him to throw more strikes, which is something they've had success with as an organization with other hurlers.