The team also announced before Tuesday night's game at Tampa Bay that infielder Brett Lawrie was transferred from the 15- to the 60-day disabled list.
Morrow had been sidelined because of an injured right finger since early May, while Johnson missed a month with a strained left hamstring. Lawrie went on the DL in early August with an oblique injury.
Second baseman Ryan Goins, outfielder Anthony Gose, right-hander Kendall Graveman and left-hander's Sean Nolin and Daniel Norris were recalled from Triple-A Buffalo. Outfielders Dalton Pompey and George Kottaras had their contracts purchased from Buffalo.