The Reds reinstated Johnson (elbow) from the 15-day injured list Monday.
Johnson gave up one run in a one-inning, 17-pitch rehab appearance with Triple-A Louisville on Friday, and that was apparently all the Reds needed to see from the right-hander on the farm before adding him back to their bullpen. Before hitting the shelf May 30 due to right elbow inflammation, Johnson had been working in a setup role for the Reds and posted a 3.27 ERA and 1.23 WHIP while collecting four holds, one save and two wins in 24 appearances.