Oakland also added outfielders Luis Barrera and Skye Bolt, and right-handers Grant Holmes and James Kaprielian to the 40-man roster on Tuesday. Oakland now has 39 players on the roster.
The 25-year-old Anderson made his major league debut last season. He went 1-0 with a 6.35 ERA in six outings spanning 11⅓ innings for the Pirates. In four career minor league seasons, he is 21-13 with a 3.24 ERA in 120 appearances, including 22 starts.