Hartlieb has the ability to decline the outright assignment and elect free agency, but he already accepted an outright assignment earlier this month and could do so again. The reliever has allowed nine runs with a 6:9 K:BB over 13.1 frames during his time with the Athletics this season.

Hartlieb had his contract selected from Triple-A Las Vegas on July 18, 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 following his promotion. The team acquired right-handed reliever Scott Blewett from the Cardinals on Sunday, and he'll replace Hartlieb on the 40-man roster. If Hartlieb goes unclaimed on waivers, he'll likely report to Triple-A Las Vegas.