Ramirez cleared waivers after posting a 4.91 ERA in 11 innings of work over two stints with the big league club. He allowed nine hits and 10 walks while striking out 10 over that span.
Ramirez was designated for assignment to make room for outfielder Jack Cust, who is batting .316 (6-for-19) since being called up from Sacramento.
The A's also announced Friday they have released right-hander Chad Gaudin. Gaudin, who had been with the A's since Opening Day, was originally designated for assignment Sunday.
Gaudin had an 8.83 ERA in 12 appearances (17 1/3 innings pitched), which was the highest figure in the American League at the time of his designation. He was hit hard in his final two appearances, when he gave up a combined nine runs (eight earned) over 4 1/3 innings of work.
Since the departure of Ramirez and Gaudin, the A's have reshaped the bullpen by adding southpaw Cedrick Bowers and Triple-A starter Vin Mazzaro.
Alden Gonzalez is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.