There is no return date for Brumbies star David Pocock, but coach Dan McKellar remains hopeful he will travel with the team next week to South Africa.
The 30-year-old will miss a second-straight Super Rugby game due to a persistent calf injury.
Pocock sat out the Brumbies' last game on April 28 in the hope he would be right to take on the Melbourne Rebels on Saturday night after the ACT team's bye last week.
But it has been a slower-than-expected recovery for the ace flanker and he is no certainty of heading overseas for games against the Lions and Bulls.
Pocock has played only four games this year after returning from a 12-month sabbatical with the start of his season delayed because of knee surgery.
"If you throw him out there to play this weekend, you risk him not being in Africa. We've got to get him to 100 per cent and he's not quite there," McKellar said on Thursday.
"If 'Poey' was in a position where he I thought he could play, I would play him (now) but he's not."
His absence is a big blow to the Brumbies ahead of a season-defining game against their Australian conference rivals.
A second loss to the Rebels this season would put a further dent in the Brumbies' finals hopes.
But they do have some experience returning to the starting XV.
Co-captain Christian Lealiifano was rested from the past two games, mainly because of his stint playing in Ireland in between Super Rugby seasons.
Lachlan McCaffrey is a surprise inclusion in the No.6 jersey considering he dislocated his elbow a month ago against the Queensland Reds.
The Brumbies will hope to get a boost from rising star Rob Valetini. He injured his knee in the first 20 minutes of the round-one clash with the Sunwolves.
Tom Banks, Henry Speight, Tevita Kuridrani, Christian Lealiifano, Andrew Muirhead, Wharenui Hawera, Joe Powell, Rob Valetini, Tom Cusack, Lachlan McCaffrey, Sam Carter, Rory Arnold, Allan Alaalatoa, Folau Faingaa, Scott Sio.
Res: Robbie Abel, Faelelei Sione, Ben Alexander, Blake Enever, Lolo Fakaosilea, Matt Lucas, Jordan Jackson-Hope, Lausii Tailauii.