Johnson developed the blister during his most recent outing, against the Rangers on June 9. He received medical attention during the game but continued pitching until he had to be removed after the fifth inning because of a high pitch count.
The 29-year-old is still searching for his first win of the season. He is 0-2 with a 5.40 ERA in six starts and previously missed six weeks because of inflammation in his right triceps.
As a result of the move, knuckleballer R.A. Dickey had his start moved up to Saturday, though he will still be pitching on normal rest because of Wednesday's rainout.
Dickey faced the White Sox in his previous outing and allowed seven runs on 10 hits over five innings. It was the third time in his past four outings that he surrendered at least six runs.
Gregor Chisholm is a reporter for MLB.com. Read his blog, North of the Border, and follow him on Twitter @gregorMLB. This story was not subject to the approval of Major League Baseball or its clubs.