The Oakland Athletics selected pitcher Neil A Sacramento on Tuesday and outrighted pitcher Bruce Billings to the minor league club.
In addition, pitcher Jerry Blevins cleared waivers and was optioned to Sacramento.
Wagner has split time with Double-A Midland and Sacramento this year, compiling a 3-4 record with a 3.26 ERA and six saves between the two leagues.
When he appears in a game for Oakland he will make his major league debut.
Billings was acquired from Colorado on June 30 in a trade for second baseman Mark Ellis. He appeared in three games for Oakland and allowed nine runs -- seven earned -- through five innings.