The Brumbies midfielder had a scan in Sydney earlier today and is expected to be sidelined for between four and six weeks.
McCabe will miss the back-to-back clashes with the All Blacks on August 18 and 25, leaving the Wallabies with yet more selection dilemmas in their backline.
The 24-year-old had been tipped to start against the World Champions, especially as Robbie Deans is without utility back James O'Connor, while Quade Cooper's lack of game time means Berrick Barnes is favourite to start at No10 rather than 12.
McCabe may only have 14 international caps to his name but his influence within the Wallaby set up should not be underestimated. Part of a five-man leadership group this year, McCabe's progress since his Wallaby debut in 2010 was one of the reasons why legendary playmaker Matt Giteau was deemed surplus to requirements.
There are no plans to replace McCabe in the Wallaby squad as things stand due to the fact that Deans still has plenty of options in that department in the shape of Mike Harris, Anthony Fainga'a, Ben Tapuai and Rob Horne.
Fainga'a and Horne are most comfortable in the No13 shirt, though, while Tapuai has spent most of his time sat on the replacements' bench at the Reds this season.
Harris became a national hero when he slotted a last-gasp penalty to help the Wallabies beat Wales in the second Test in Melbourne last month but the 23-year-old's lack of experience could be a worry when it comes to taking on the world champions.
Australia are currently enjoying their second training camp after none of their five franchises made it through to the Super 15 semi-finals.
The squad will break up again on Friday, with the final 30-man party for the Rugby Championship to be named on Tuesday, August 6. That group will then assemble in Sydney the same day.