Hughes announced his retirement Sunday, Bob Nightengale of USA Today reports.
The Padres released Hughes on Wednesday.
Hughes was designated for assignment by San Diego on Friday.
Hughes (back) was reinstated from the 10-day disabled list Friday.
Hughes was placed on the 10-day disabled list Thursday with a right rhomboid strain.
Hughes will be available for Tuesday's game against the Marlins and is slated to work out of the bullpen initially, Jay Paris of MLB.com reports.
Hughes was traded to the Padres on Sunday in exchange for minor-league catcher Janigson Villalobos.
Hughes is moving to the bullpen, the team announced Monday.
Hughes is no longer listed as the Twins' starter Wednesday against Toronto, Mike Berardino of the St. Paul Pioneer Press reports.
Hughes allowed two runs on five hits and two walks across 3.1 innings in a no-decision Sunday against the Rays. He struck out two.