Auelua will miss the match after suffering a heavy concussion against the Hurricanes last Friday.
He has been replaced in the starting XV by Peter Kimlin.
Kimlin will move to blindside flank with captain Ben Mowen returning to the back of the scrum.
Instead of adding another ball scavenger to their squad, coach Jake White has opted for extra height with 200cm lock Leon Power joining the bench.
The only other change to the Brumbies’ starting side is scrumhalf Nic White reclaiming the No 9 jersey after being rested on the bench last week.
The Brumbies can almost lock up a finals spot if they beat the Reds at Canberra Stadium.
They are eight points clear at the top of the Australian conference with just five games remaining in the regular season.
If they lose, the Brumbies and the Reds will be level with each other because Queensland has a bye next weekend.
Teams:
Brumbies: 15 Jesse Mogg, 14 Henry Speight, 13 Andrew Smith, 12 Pat McCabe, 11 Joseph Tomane, 10 Zack Holmes, 9 Nic White, 8 Ben Mowen, 7 Michael Hooper, 6 Peter Kimlin, 5 Scott Fardy, 4 Sam Carter, 3 Dan Palmer, 2 Stephen Moore, 1 Ben Alexander
Substitutes: 16 Anthony Hegarty, 17 Ruaidhri Murphy, 18 Leon Power, 19 Ita Vaea, 20 Ian Prior, 21 Robbie Coleman, 22 Tevita KuridraniReds:
TBA