The Brumbies have kept their playoff hopes alive with a 30-20 bonus point win over the Lions in Johannesburg, but it has come at the cost of another injury to Wallabies midfielder Matt Toomua.
He was forced from the field after just 24 minutes with a possible recurrence of the same high-ankle injury that had sidelined him for five weeks.
The Waratahs' 33-18 win over the Sharks in Sydney earlier on Saturday night had pushed them to the top of the Australian conference, but the Brumbies' win ensured that was short-lived.
The Lions also blew a chance to top the South African conference lead, with the Stormers having a bye and the Bulls losing to the Blues in Auckland on Friday night.
The Brumbies' four-try bonus point came in the 72nd minute, after fullback Jesse Mogg put winger Joe Tomane in the corner.