Santillan (oblique) could be activated to the major-league roster later this week, Mike Petraglia of MLB.com reports.
Santillan worked a scoreless inning as the opener in Sunday's game and will make at least one more appearance either Tuesday or Wednesday. If all goes well, the right-hander could rejoin the Reds at the end of the week. He's made two scoreless appearances with the Bats, striking out three over two innings.