Hacker, who was signed in the offseason, was 1-0 with a 0.00 ERA, allowing four hits with 10 strikeouts in two starts for Rochester. Hacker will join the Twins' bullpen Tuesday in Baltimore.
"We need a long guy out there," Twins manager Ron Gardenhire said. "Hacker has been throwing very, very well. We're trying to revamp things."
To make room for Hacker on the 25-man roster, right-hander Alex Burnett was optioned to Rochester. Burnett made three relief appearances for the Twins, allowing one run in 2.1 innings pitched.