Cortes will serve as the Athletics' designated hitter and No. 6 batter in Sunday's game against the Tigers.
The left-handed-hitting Cortes had started just once in the last eight games, though he had a bit of an unlucky runout with the Athletics facing just one right-handed starter during that stretch. Cortes should be fairly secure in a strong-side platoon role until the Athletics get at least two of Zack Gelof (knee), Denzel Clarke (hamstring) and Joshua Kuroda-Grauer (testicle) back from the injured list.