Flaherty was optioned to Triple-A Memphis on Wednesday, Joe Trezza of MLB.com reports.
The Cardinals needed to clear a roster spot for Adam Wainwright (hamstring) to return from the disabled list, and Flaherty was a logical choice since he's unavailable for a few days following Tuesday's start. The 22-year-old pitched well, allowing just one run in five innings of work in the no-decision. He will likely be the first pitcher called back to the majors if another injury strikes the big-league rotation.