Ruiz was outrighted to Triple-A Las Vegas on Thursday, John Shea of the San Francisco Chronicle reports.
Ruiz (0-1) was charged with the loss and a blown save Thursday against the Nationals, allowing four runs (three earned) on two hits and a walk over two-thirds of an inning. He struck out one.
Ruiz was recalled from Triple-A Las Vegas on Wednesday.
Ruiz was optioned to Triple-A Las Vegas on Friday.
Ruiz had his contract selected by the A's on Friday.
Ruiz was reassigned to minor-league camp Sunday, Jane Lee of MLB.com reports.
Ruiz was suspended 10 games for doctoring the baseball during Monday's game with High-A Stockton.