Captain Adam Coleman has failed to train with the Melbourne Rebels, putting his selection in doubt for their crunch Super Rugby final-round clash with the Highlanders.
Two other Wallabies stars nursing injuries - halfback Will Genia (broken arm) and Dane Haylett-Petty (knee) - took part in Wednesday's run.
However, lock Coleman (adductor strain) didn't partake, less than 24 hours before the team fly to Dunedin ahead of Saturday's game.
The tough 26-year-old's presence would be invaluable for the eighth-placed Rebels in a match that must win to ensure they reach the finals for the first time.
If they lose, they are exposed to being passed by the Brumbies or the Sharks.
The trio will undergo further fitness testing before decisions are made on their availability. The team is unveiled on Thursday.
Coleman and Genia haven't played since being struck down during last month's Test series loss to Ireland.
Haylett-Petty hyper-extended his knee during last Friday's 37-23 loss to the Queensland Reds.
Captain Tom English was delighted to see Coleman take a leadership role at practice and said the 23-Test veteran's words will be ringing in his team-mates ears if he can't play.
"He's quite an enforcer and really drives the standards," English said.
"He gets in the young locks' ears and tells them what to expect and how to prepare for a big game like the one at the weekend."
Despite the high stakes, English said there has been a deliberate effort not to place pressure on the young players in particular.
He wants them to express themselves in what should be a high-tempo encounter under the roof of Forsyth Barr Stadium.
They have put twin losses to the NSW Waratahs and Reds behind them and concentrated on what worked best for them during a three-match winning streak leading up to the June international break
"The beautiful thing is our destiny is still in our own hands," English said.