The 31-year-old Hughes had been on the DL since complaining of a "dead feeling" in his pitching shoulder on May 21. He allowed one run in three innings during three rehabilitation appearances with Triple-A Rochester.
Hughes has been mostly a starter since 2009, but manager Paul Molitor said Hughes will work out of the bullpen when he returns.
Left-hander Craig Breslow was put on the 10-day DL with rib cage soreness. He is 1-1 with a 5.28 ERA in 27 games.