Ayala, 35, was 5-5 with one save in three chances and a 2.64 ERA in 66 games with the Orioles in 2012. He had a 2.09 ERA in 52 games with the Yankees in 2011. Ayala is 1-0 this season, allowing two runs in two innings with Baltimore.
Ayala restores experience and depth to an Atlanta bullpen that is expected to be without left-hander Jonny Venters for at least another month. Venters was shut down on April 2 after receiving an injection in his sprained left shoulder.
Venters, on the 15-day disabled list, had been one of the team's top setup men for closer Craig Kimbrel. Venters received the injection after he was examined by Dr. James Andrews, who performed ligament-replacement surgery on Venters' elbow in 2005.