Toomua will arrive in Johannesburg on Tuesday Australian time in preparation for the clash to play the Lions in a make-or-break contest at Ellis Park.

The Brumbies are still reeling after a devastating one-point loss to the Cape Town Stormers on the weekend and Larkham has urged the team to keep the faith in its systems to turn tight losses into crucial wins.

The Brumbies' scrum cracked under the pressure of the best set-piece in Super Rugby and their weakness was ruthless exploited in a 25-24 win.

Toomua's arrival won't ease the pressure on the scrum, but the Wallabies playmaker will be a welcome sight in the Republic with the Brumbies' finals hopes dangling dangerously close to disaster.

Toomua has missed the past four weeks with an ankle injury but is set to be injected straight into the starting side to play the Lions.

The Brumbies (33 points) hold a one-point lead in the Australian conference ahead of the NSW Waratahs (32 points) and the Melbourne Rebels (29 points).

Only one will clinch a guaranteed finals berth and the Waratahs and Rebels have a game in hand in the last five weeks of the regular season.

The one-point loss to the Stormers was a cruel blow to the Brumbies' year and added more pain to a season which has been punctuated by five losses by five points or less.

It leaves the Brumbies' play-off hopes in danger of disappearing and the season becoming a year of 'what ifs'.

"You've got to stay with it; had those tight games gone the other way we're on 49 points on the ladder," Larkham said.

"We know we're almost there. You change a few things but don't make wholesale changes.

"It's definitely a frustrating season, we're lucky to be on top of the Australian conference. We've said 'what if'. But the season's not over.

"We'll look back at moments that could have turned the season for us."

The Brumbies' scrum started to fall apart at Newlands, particularly in the second half with referee Stuart Berry forced to continually penalise the forward pack for set-piece technical problems.

Wallabies loosehead prop Scott Sio is still at least two weeks away from returning after a knee injury.

But they face a massive task to rebuild some respect at scrum time after being demolished.

Their scrum problems allowed the Stormers to kick penalty goals and their only try came off the back of sustained pressure close to the Brumbies' line.

The 19-5 penalty count was skewed because of the deficiencies in the forward pack.

"The Stormers have one of the best scrums in the competition ... the dominance they had in the scrum hurt us," Larkham said.

"They were better than us in the scrum, there's no hiding from that."

Brumbies hooker Stephen Moore said the team had to be brutally honest in their post-match appraisal of their disappointing performance.

"The effort is there, that's a starting point. We've got to have some honest conversations around the scrum, no one part of the game is bigger than the other," Moore said.

"Part of the culture of the team is being honest with each other. We're just going to have to work on it. We've certainly had enough admirable losses ... we're not going to sugar-coat it. It's a loss and we're gutted."

AT A GLANCE

CAPE TOWN STORMERS 25 (Schalk Burger try; Demetri Catrakilis 5 penalties, drop goal, conversion) bt ACT BRUMBIES 24 (Joseph Tomane, David Pocock tries; Christian Lealiifano 3, Jesse Mogg penalties; Christian Lealiifano conversion) at Newlands on Sunday morning Australian time. Referee: Stuart Berry.