Will Genia will miss the remainder of the Rugby Championship and will be sidelined for at least six months after rupturing the ACL in his right knee.
Genia's injury follows that of regular captain James Horwill (hamstring) and the man who replaced him, David Pocock (knee), who were both already ruled out for the rest of the series.
The scrum-half, who underwent scans on Sunday at a Perth hospital, will be replaced for the match against Argentina on the Gold Coast next Saturday by veteran half-back Brett Sheehan.
"I took the high ball, it twisted and I heard a few cracks," Genia recalled after the 26-19 victory.
Nathan Sharpe is set to assume the captaincy.