Blanton, 33, was originally drafted and developed by the Athletics. He broke in with the team in 2004 and went 47-46 with a 4.25 ERA (101 ERA+) in parts of five seasons with Oakland before being traded to the Phillies in 2008.
In 20 starts and eight relief appearances for the Angels in 2013, Blanton went 2-14 with a 6.04 ERA (62 ERA+). He got hammered in spring training (7.08 ERA) and was released last week despite the team's pitching needs.
The A's lost Jarrod Parker for the season and A.J. Griffin for a few weeks, so it wouldn't take much for Blanton to get called up to the big league team.