The pair suffered injuries during the ACT franchise's 29-26 loss to the Melbourne Rebels last week and will not be risked on Friday night at GIO Stadium.

It is a major blow for the Brumbies, who are desperate to get their season back on track after slumping to a 1-3 record.

Brumbies coach Dan McKellar said the duo could miss up to two weeks.

McKellar confirmed their absences would count as a rest, with all Australian Super Rugby coaches having to sit out Wallabies players at times during the season ahead of the World Cup.

Prop Alaalatoa has been cleared of major damage to his wrist while Pocock is trying to manage a niggling calf issue which has troubled him since January.

Unheralded tighthead prop Leslie Leuluaialii-Makin will replace Alaalatoa in the front row, with Tom Cusack slotting into Pocock's No.7 jersey.

McKellar is hoping for a similar result to the last time Pocock missed a game, where the Brumbies demolished the Chiefs 54-17 three weeks ago.

A third-straight loss would almost sink the Brumbies' finals hopes not even a third of the way through the season.

The Rebels are top of the Australian conference with a 3-0 record while the Waratahs are second at 2-1 after defeating the winless Queensland Reds last week.

McKellar said his team was motivated to take down the Waratahs for the second straight time after the Brumbies won the final-round clash last year.

"It's the Tahs at home, an opportunity to get stuck into the New South Welshmen, what more do you need to get excited," he said on Wednesday.

"You're playing against NSW whether it's rugby, marbles or whatever. Yeah I'm a Queenslander, but I'm a Brumbies man now and there's a dislike for the Tahs."

After being rested last week, No.8 Lachlan McCaffrey is back in the starting side, while winger Andy Muirhead and centre Tom Wright make way for Lausii Taliauli and Irae Simone respectively.

Brumbies: Tom Banks, Henry Speight, Tevita Kuridrani, Irae Simone, Lausii Taliauli, Christian Lealiifano (capt), Joe Powell, Lachlan McCaffrey, Tom Cusack, Rob Valetini, Sam Carter, Rory Arnold, Leslie Leuluaialii-Makin, Folau Fainga'a, Scott Sio. Res: Josh Mann-Rea, James Slipper, Tom Ross, Murray Douglas, Pete Samu, Ryan Lonergan, Jordan Jackson-Hope, Mack Hansen.

Australian Associated Press