Triple-A Las Vegas placed Acton on its 7-day injured list Wednesday due to an unspecified injury.
Acton's move to the IL came three days after he was blasted for seven earned runs on five hits and two walks in just one inning for Las Vegas. The Athletics haven't provided an explanation for Acton's injury, but even if it proves to be minor, it'll push back any potential return to the big leagues for the right-hander. Acton made five relief appearances for Oakland earlier in the season, giving up eight earned runs over 5.2 innings.