Wallabies number eight Wycliff Palu looks set to miss Saturday's second Test against France due to an ankle injury.
The Waratahs loose forward sat out training on Monday to nurse the long-term injury that he carried into last weekend's opening Test against Les Bleus in Brisbane.
Coach Ewen McKenzie is unlikely to risk Palu in the second Test in Melbourne on Saturday if the injury continues to trouble him on Tuesday, opening the door for in-form Western Force number eight Ben McCalman.
With Stephen Moore (knee) and debutant lock Sam Carter (ankle) already ruled out, former skipper James Horwill and hooker Tatafu-Polota-Nau are in line to receive recalls to the starting XV. The Force's Nathan Charles looks set to make his Test debut off the bench.
McCalman has been in outstanding form and the Wallabies would lose little with his addition to the back of the scrum.
"He's been very consistent and very solid and has led the way in a lot of key areas," said McKenzie.
"He fits the physical profile of what we think is required."
Horwill trained alongside his Reds teammate Rob Simmons on Monday was also praised for his contribution off the bench in Brisbane.
"The cards didn't fall his way but it didn't stop him contributing to the team and that's what you want," McKenzie told AAP.