Flanker Chris Alcock (thigh gash) is in doubt for this week, while Wallabies' lock Rory Arnold (shoulder) is the other addition to the injury list.
Both men are expected to be in the selection mix for the home quarter final knockout match on July 21.
Irrespective of their availability for this week, Larkham is expected to name a much different side to the one that started against the Reds.
With the Chiefs looming as a potential playoff opponent the following week, neither side is likely to reveal their full hand on Saturday.
"I think both sides are probably going to try and feel each other out this weekend," Brumbies' halfback Joe Powell said.
"It's not the big important one this weekend, the next weekend is the one you want to win.
"But still for us, we need to sort our stuff out from last weekend."
Powell said the Brumbies played pretty terrible footy against the Reds, but was adamant the performance hadn't dented their confidence.
"I don't think so, everyone was just a bit off, everyone has an off game, I think we believe in ourselves still," Powell said.
Brumbies New Zealand-born five-eighth Wharenui Hawera will be going back to his home town this weekend.
"I'm definitely excited to go home and see family and play in Hamilton,' Hawera said