Joe Tomane has been ruled out for up to eight weeks after sustaining a knee injury against the Crusaders last weekend.
The Brumbies wing collided with Crusaders flank Matt Todd in the 76th minute and scans revealed he suffered medial ligament damage to his right knee.
Tomane is the Brumbies' top try-scorer with six this season and the joint second-highest with Sergeal Petersen.
Meanwhile, Brumbies captain Stephen Moore is nursing a calf muscle injury and will undergo rehabilitation throughout the week in a bid to be fit in time to lead the team against the Highlanders in Invercargill on Saturday.
Photo: Ashley Vlotman/Gallo Images