Ramirez was called up from Triple-A Nashville on Saturday, Jane Lee of MLB.com reports.
The 27-year-old right-hander was brought up to help offset the placement of Santiago Casilla on the disabled list due to a right shoulder strain. Ramirez had just been claimed off waivers by the Athletics on May 20 after being let go by the Blue Jays, and he'd fired two scoreless innings in his only appearance for the Sounds prior to his promotion. Ramirez also logged two big-league appearances this season while with Toronto, allowing one earned run on a hit and five walks while also recording three strikeouts across 2.2 innings.