A growing number of injuries for the Brumbies now includes Wallabies back Matt Toomua after the third Test against France.
Toomua is out for an unspecified amount of time after straining an abductor muscle.
Toomua started all three Tests for the Wallabies at inside centre ahead of Kurtley Beale, but was forced off after 50 minutes in Sydney.
Brumbies director of rugby Laurie Fisher admitted that the number of key injuries was a big test for the squad, as they seek to return to the Super Rugby Final after losing last year to the Chiefs.
"Moore's out, Carter's out, Mann-Rea potential, Toomua has adductor strain, McCabe is about 50-50 at best ... put them together and it's going to be a big week," Fisher told the Canberra Times.
"We'll rely on what we do, and the depth of our squad. It will test character and spirit.
"Whatever 15 or 23 we put out there, we'll have a red-hot crack. We just have to wait to see who we can put on that team list.
"We might get a whole heap of good news, we might get a whole heap of bad news, or we might get a bit of both.
"We've got four players who are on the doubtful list at this stage ... it's going to be a massive test for the work we've done in the last two or three years."