Morales, 25, split last season between Colorado and Boston, and he finished the year 1-2 with a 3.69 ERA in a career-high 50 appearances out of the bullpen.
The southpaw has spent parts of five seasons in the big leagues -- with the Rockies from 2007 until May of '11, when he was acquired by the Red Sox.
Morales also set career marks for innings pitched (46 1/3), strikeouts (42) and holds (10). He held opponents scoreless in 28 of his 36 appearances out of Boston's bullpen.
Morales is 8-12 with 10 saves and a 4.61 ERA in 138 career Major League games.