Phillips elected free agency last week, refusing an outright assignment to the minor leagues from the Chicago White Sox,
Phillips was 0-1 with a 3.45 ERA in 19 games with Baltimore and Miami from 2011-13. He appeared in 16 games with the Orioles in 2011-12.
Phillips could make Baltimore's opening-day roster if left-hander Brian Matusz, who is sidelined with a back injury, begins the season on the disabled list.
To make room for Phillips on the 40-man roster Wednesday, Baltimore designated left-handed pitcher Chris Jones for assignment.