The Padres optioned left-hander Frank Garces to Double-A San Antonio.
Cashner had been on the DL with right shoulder soreness since June 23. He allowed six runs and struck out seven in 7 2-3 innings in three rehab starts with Single-A Lake Elsinore and Triple-A El Paso.
Cashner is 2-6 with a 2.36 ERA for the Padres this season.
Garces has worked three scoreless innings since making his major league debut Tuesday night at Dodger Stadium.