Johnson (back) has been activated from the disabled list at Triple-A Iowa.
Johnson missed about six weeks with the lat injury and has managed just four starts with a 5.17 ERA and 1.71 WHIP thus far in 2016. He was one of the Cubs' top prospects entering the season and was considered a possibility for a midseason call-up, but he needs to show he's healthy before dreams of the next level can be entertained.