The A's placed reliever Eric O'Flaherty on the 15-day disabled list with a strained left shoulder as part of a series of roster moves Saturday.
Outfielder Cody Ross was designated for assignment. Reliever R.J. Alvarez and outfielder Billy Burns were recalled from Triple-A Nashville to take their roster spots.
Also, outfielder Alex Hassan was claimed off waivers from Texas and optioned to Nashville. It's the third time Hassan has joined the A's organization since early in the offseason.
O'Flaherty has struggled to an 11.57 ERA this season, and only recently did it surface that he had a shoulder issue. The lefty came back from reconstructive elbow surgery midway through last season.
Burns made the Opening Day roster before being optioned April 8. He was hitting .315 with Nashville before being recalled. Burns is leading off and playing center field Saturday night against Texas.
In being designated for assignment, Ross is removed from the 40-man roster. The A's have 10 days to trade or release him, or send him to the minors if he clears waivers.