Morahan scored a stunning solo try and made two try-saving tackles for the Reds in a 22-12 loss to the Lions in a tour match on Saturday night.
The 23-year-old Morahan, a sevens star who plays fullback or wing in the 15-a-side game and has one Test cap for Australia, is expected to join the 31-man Wallabies squad on Wednesday to bolster an outside back division that includes Digby Ioane, Israel Folau, Nick Cummins and either Kurtley Beale or James O'Connor, depending on who gets selected at flyhalf.
Tomane, who injured a toe on his left foot at training on Tuesday, will remain with the squad.