The Athletics reinstated Alexander (shoulder) from the 15-day injured list Wednesday.
Left rotator cuff tendinitis sent Alexander to the injured list Aug. 20, and rather than heading to the minors for a rehab assignment, he'll now rejoin Oakland's bullpen following a minimum-length stay. The 35-year-old southpaw has been strong all season, and he's given up just two earned runs over 10 innings since the All-Star break. Joe Boyle was optioned to Triple-A in a corresponding move.