The move was made prior to Tuesday's series opener against the Yankees.
The 28-year-old Simon went 1-1 with a 1.59 ERA, five walks and 14 strikeouts in four games (three starts) for Norfolk. Mickolio was recalled on April 15 and recorded a 7.36 ERA over 3 2/3 innings, with three walks and four strikeouts in three games.
Brittany Ghiroli is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.