The Athletics designated Brooks for assignment on Sunday.
Brooks joined Oakland's rotation in mid-May but won't retain his place on the 40-man roster after he made four starts and posted a 5.82 ERA, 1.62 WHIP and 10:6 K:BB over 21.2 innings. Luis Medina (knee) was reinstated from the 60-day injured list in a corresponding move and will start Sunday in Atlanta.