In another move before Sunday's game against Washington, the Reds optioned right-hander Curtis Partch to Triple-A Louisville to make room on the 25-man roster. Hannahan was in Cincinnati's starting lineup at first base.
The 34-year-old Hannahan hit .300 over 12 games during a rehab assignment with Single-A Dayton and Triple-A Louisville. On Saturday, he joined the Reds and took batting practice and ground balls at first base. He is in his second season with the Reds.
Partch is 1-0 with a 0.00 earned-run average in five games over four stints with Cincinnati this season.