Tapia was optioned to Triple-A Las Vegas on Wednesday.
Tapia made two relief appearances for the Athletics after being called up in late May. He tossed a scoreless inning during his first outing but will be sent down after giving up four runs on six hits in one-third of an inning against the Red Sox on Saturday. Jared Koenig's contract was selected as part of a corresponding move, and he'll start Wednesday's game in Atlanta.