The Athletics designated Hartlieb for assignment Sunday, Jason Burke of Roundtable.io reports.
After being called up from Triple-A Las Vegas on July 18, Hartlieb surrendering four runs on six hits and six walks while striking out three batters over 4.2 innings in four appearances with the big-league club. He'll cede his spot on the 40-man roster and in the bullpen to right-hander Scott Blewett, whom the Athletics acquired in a trade with the Cardinals.