Australia A coach Laurie Fisher said he won't rush back the 2007 Australian Super 14 Rookie of the Year, despite admitting that he desperately wants to win the PNC.
"We've got some important games coming up and we'd like Lachie to be available, however his recovery is of utmost importance at this stage," Fisher said.
"There's no point in rushing an injury like this, particularly as we've got good depth within the squad.
"However Lachie has done some good things in the tournament so far and it would be a shame if he were to play no further part."
In better news for Fisher on a domestic level, his Brumbies have snapped up the services of Peter Betham, signing the talented youngster to a two-year deal on Monday.
"Peter's been a strong performer at schoolboy and under-19 level," Fisher said. "He's a player with good size and athleticism and we're looking forward to him developing his game with us over the next two seasons."
Betham, a teenage star, is tipped to develop into a full back over the coming years.