Hunter Greene is expected to come off the injured list on Friday to open the series against the National League Central Division-leading Chicago Cubs on Friday.
Greene left the mound on May 7 after feeling a tight right groin while warming up for the fourth inning in Atlanta.
Chase Petty, who replaced him in the starting rotation, was sent back to the Louisville Bats on Wednesday morning as the Reds reinstated Ian Gibaut from the injured list.