Ferguson (oblique) walked one over a scoreless inning for Triple-A Louisville on Friday.
Ferguson, who also threw Thursday, worked on back-to-back days for the Bats, which is typically a final box to be checked off for a reliever before coming off the injured list. The left-hander has made four appearances combined between Louisville and Double-A Chattanooga. The Reds' bullpen has fallen apart in May (8.47 ERA) and could use Ferguson as soon as possible.